Hold on there guys; You're not going to be able to just walk to the bridge. I made a couple of crappy maps just to give you a general idea of where things are. Your eventual goal is to get to the unmarked room behind the bridge. The general is probably in there. There are a couple ways to get there but I'll let you decide which way.
The first way is to go through the bridge itself. This is likely to get you a pretty big firefight, on top of alerting most of the ship to your presence. You can still pull it off safely, assuming you can get off the ship fast enough.
The second way is to go out into space using an airlock on the underside of the ship. Of course, that is only an option if you can find enough spacesuits for all of you to fit into. There are bound to be a few around, since the airlock is most likely used for engine maintenance. From there, you would use the escape pod on the backside of the bridge as an airlock to get into that unmarked room.
The third way is to go around the exterior of the ship (as described above), blow a hole in the outside of the ship, and throw a grenade in there. The problem with this is that you won't be sure that there was ever anything in there. You could, if you wanted, proceed from there to the bridge to make sure you really did get your target.
Your decision. As of now, you are on the level that is colored blue on the map.
Map #1...