You say Black Ops, so I would guess likely something like a Glock 17 or 26, or SIG-Sauer variety, maybe even a Beretta 92 if you're talking handguns (especially silencers). If they have assault rifles, my guess would be something more like an M4, H&K MP5, maybe an FN P90, or an AK74.
Check this out too:
Internet Movie Firearm Database
In the end though, the sound can be whatever you want it to be as long as it fits the style of gun (pistol versus rifle) and feels right - some guns may look like you'd hear more of the mechanics, whereas others you see may feel more like a solid 'boom'. It's a taste thing, designing the sound of each one so the feel right and fit the character. I'd opt for the idea of not taking it quite so literally as long as you follow the above mentioned general ideas.
Same goes for the ricos/impacts. giving the ricos an interesting character could flavor up the scene and give it a more claustrophobic feel. If we see the metal chassis, maybe play them bigger sharper metal with interesting decays (like in a submarine), but if it's a more finished interior with carpeting, etc it might be good to play more muted but thumps, with some metal showing throw on occasion. Again, going by what you see and what feels right. It's the kind of thing nobody can really teach, you have to feel it out - some can and some have trouble. Studying films of similar nature might give you some ideas to elaborate upon too.
As for the interior, definitely pressurized - a very distinctive sound compared to a house room. It's going to usually have a thich (mid-hi) air quality and usually some sort of distinctive air whine, often with a slight metallic quality. Think of a server room, but just the air/fans. Frank Bry has an outstanding set of well-recorded Airplane interiors on his Recordist site. In my opinion I would never just drop one of those in and call it a day, but it serves as fantastic source material palette to build upon and layer. Think of other source material for which air moves or has an interesting whine - fans (even small ones), jets, HVAC units, hiss, roadside electrical boxes (these have such interesting sounds!), blow dryers, fridge int air. Lots of source material to pull from.
I think you are not suffering from uncertainty, but rather not committing to trying a specific idea ;)
P.S. Please, for the love of God, avoid the well-over-used silencer zip! ;) If there are silencers going on, make it your own and design something special. It will be worth it! Inception has an interesting take on a silencer at the beginning which is very different than the cliche sound, as do the silencer(s) in The Iceman and the TV show Nikita. I'm sure there are many other examples too, but.... please don't use that zip silencer!
