You have to win the battle against the waves of mercs and destroy the gunship. Keep an eye on the yellow "Garrus Life Signs" meter in the lower right hand corner of the screen. If it's going down, he's being shot and you need to protect him.
Archangel from Mass Effect is Garrus Vakarian
Yes, he will rejoin the party as part of the storyline.
No. He (can, if he survives a certain mission) be in your party, but you will not be able to play as him.
'Archangel' is the nickname that Garrus the turian used, during his time on Omega, during the events of Mass Effect 2.
(1) Haven't played it, so I dunno. (2) Garrus. I haven't tried many other people, but everyone else I personally think sucked. (3) Still Garrus. It's pretty cute. /)^3^(\ I haven't tried for the women. I only play AS a woman. Kelly kept hitting on me though. o.O
You won't be able to import your save game from ME1.
Thane, Garrus, Jacob, Miranda, Tali, Legion, Grunt, Jack, Mordin, Samara/Morinth. Those are the normal ones. If you get the downloadable ones you can also add Zaeed and Kasumi.
It just effects some interactions and choices in the game.
If he died in Mass Effect 1 then he is not in Mass Effect 2. If he survived Mass Effect 1 he shows up in Mass Effect 2 but he can not be killed.
Do the missions that say "recruit the (insert class type)"
Mass Effect 2 is a 15.
If you don't import a save game from Mass Effect, you will automatically choose the character of the opposite gender to survive. If you play Mass Effect first, though, you can choose if you want Ashley or Kaidan to survive. So to play Mass Effect 2 as a female and with Ashley alive, you would have to play Mass Effect and let Kaidan die on Virmire.