Stupid newbie questions about ME2

Is there "party banter" like in DA? Jacob and Miranda made occasional comments, but so far they always pertain to whatever mission we are on. 

Are there any missions that don't center around sneaking around and shooting things? For instance, missions based more around dialogue or exploration?

If Shep dies in combat, does player control move to a party member as it does in DA? Or do you need to reload the game at that point? (I know health regenerates when Shep is behind cover, but just in case I decide to get reckless one day...)

I chose to play as a sentinel. Is there anything major I should know to make the best use of this class?

Speaking of which, I have a little combat drone that doesn't seem to do anything. It just floats there for a bit, and doesn't seem to attack anyone. What am I missing?

Is there any way to increase my inventory so I can carry more of those ammo cylinders I keep finding all over the place?

What about all the upgrades I've been finding that need an engineer or someone in order to upgrade them? Where do I get this engineer? Is it Mordin?

Do the hacking mini-games get harder as Shep levels up?

Are there recommended levels for different areas, or do enemies scale?

How to I get my squad's loyalty? Does it just build up or down as the game goes? Or is it tied to specific missions?

Can I return to old locations after I've moved on to a different mission? For example, after I leave Omega with Mordin, can I return there later in the game?

And most importantly, how can I ensure that Jacob will end up in Shep's pants?   (Yes, she fits the qualification of being female.)

Is there "party banter" like in DA? Jacob and Miranda made occasional comments, but so far they always pertain to whatever mission we are on.

Not quite, there's some character interaction but not quite like DA or anywhere near as much. Certain characters don't even acknowledge each other's existence(ala Grunt and Thane for instance

Are there any missions that don't center around sneaking around and shooting things? For instance, missions based more around dialogue or exploration?

Yes,Thane and Samara's loyalty missions. Also the first portion of Kasumi's LM doesn't involve pew pew.

If Shep dies in combat, does player control move to a party member as it does in DA? Or do you need to reload the game at that point? (I know health regenerates when Shep is behind cover, but just in case I decide to get reckless one day...)

Shepard dies = you reload from checkpoint. There's no playing as party members(sadly)

I chose to play as a sentinel. Is there anything major I should know to make the best use of this class?

Been quite a while since i played this and only played sentinel once, so no help here im afraid.

Speaking of which, I have a little combat drone that doesn't seem to do anything. It just floats there for a bit, and doesn't seem to attack anyone. What am I missing?

Is it a party member's drone? The Sentinel doesn't have one afaik

Is there any way to increase my inventory so I can carry more of those ammo cylinders I keep finding all over the place?

There's a set amount of heat sinks that you can carry that can't be upgraded.

What about all the upgrades I've been finding that need an engineer or someone in order to upgrade them? Where do I get this engineer? Is it Mordin?

There's a terminal in Mordin's room(that requires that he's already recruited to be able to use) where you can get these upgrades, which cost resources(that you get from planet scanning)

Do the hacking mini-games get harder as Shep levels up?

No

Are there recommended levels for different areas, or do enemies scale?

They scale

How to I get my squad's loyalty? Does it just build up or down as the game goes? Or is it tied to specific missions?

After the mid-point of the game(which is the Horizon mission)you'll get notified when loyalty missions are available for a companion(the DLC characters (Zaeed and Kasumi) are exceptions and theirs can be done prior to Horizon if you so choose). Note that there are some loyalty missions where you can fail to get said character's loyalty depending on what you do despite doing the mission.

Can I return to old locations after I've moved on to a different mission? For example, after I leave Omega with Mordin, can I return there later in the game?

Omega, like Illium and the Citadel are hubs that you can revisit any time prior to the final mission.

And most importantly, how can I ensure that Jacob will end up in Shep's pants? (Yes, she fits the qualification of being female.)

Pick the flirty options and do his loyalty mission(which can't be failed) and you'll nab yourself some Alabama black snake for your femshep.

Is there "party banter" like in DA? Jacob and Miranda made occasional comments, but so far they always pertain to whatever mission we are on.

This changes over the 3 games of the trilogy.  In ME1, it's also very limited and must be manually triggered by the player.  In ME2, it's pretty much non-existent.  In ME3, there is a significant amount of squad banter.

I chose to play as a sentinel. Is there anything major I should know to make the best use of this class?

There is a section here on the forums that discusses various character and squad mate builds for all 3 games.  You may want to go to that section and just open the top pinned thread... which gives links to the various threads in the section sorted by game and then class.  (Are you sure you're not an engineer?  Sentinels don't have the drone and you probably don't have a squad mate yet that has a drone... Tali or Legion.)

Speaking of which, I have a little combat drone that doesn't seem to do anything. It just floats there for a bit, and doesn't seem to attack anyone. What am I missing?

You'll be able to add skill points into your drone as you level up that will alter it's characteristics.  Advice for the most effective evolution of it are in the thread mentioned above.

Is there any way to increase my inventory so I can carry more of those ammo cylinders I keep finding all over the place?

You can purchase an Off-Hand Ammo Pack from one of the merchants on the Citadel that will increase your ammo loadout by 10% or 15%.  That's the only upgrade to this that I'm aware of.  It is an armor piece, so you do have to equip it at the armor terminal (in Shep's cabin).  Also, with a little practice, most people don't find it worth the credits you pay for it.

Some of the weapons you'll collect later on do have larger mags. 

There is a bit of a cheat - If you're really pressed for ammo after a battle, just save at that point and reload.  Quite often some of the placed ammo lying around will respawn and you can refill then.  Ammo dropped by your kills, however, will not respawn, so make sure you collect whatever is there first before doing the save and reload.

It also helps to ensure that you reload your gun just before picking up ammo.  If you have a partially empty clip in the mag when you collect, that clip won't fill.

What about all the upgrades I've been finding that need an engineer or someone in order to upgrade them? Where do I get this engineer? Is it Mordin?

Do the hacking mini-games get harder as Shep levels up?

No, they stay about the same throughout the game.  You can purchase a Bypass Module and a Hacking Module to slow the clock down on them to make them easier, though.  Again, these are upgrades that most people find are not really worth the price.  You can also do a save just before opening up the hack or bypass and reload to try again if you blow it.

Are there recommended levels for different areas, or do enemies scale?

Enemies do scale.  Some missions can seem quite a bit tougher if you happen to bring the "wrong" squad with you.  You'll get the hang of anticipating who you need with you from the mission descriptions or you can look up the recommendations in the Wiki (but there are major spoilers when you do that).

How to I get my squad's loyalty? Does it just build up or down as the game goes? Or is it tied to specific missions?

Can I return to old locations after I've moved on to a different mission? For example, after I leave Omega with Mordin, can I return there later in the game?

You can return to the hubs - Omega is one of those; but you cannot go back into the mission areas after completing a mission.  Whatever loot you've missed, you miss out on.

And most importantly, how can I ensure that Jacob will end up in Shep's pants? (Yes, she fits the qualification of being female.)

There is a romance guide online that gives specifics on this... just google "Mass Effect 2 romance guide" and it will step you through it.