Cobalt SS Network - Stage 2 belt and 2.9" pulley?

Hey guys, been a member since August when I picked up my 2005 ss/sc, since then I haven't been very active since I'm currently in graduate school and it's been killing me. Anyways, I figured one day I might like to make the move to stage 2, but since money is always a little tight during school I've been holding off. Then yesterday I was going down the highway and saw a saturn ion redline and naturally had to pull up next to him to scope it out. He ended up rolling the window down and asked me if I wanted to follow him to the mall parking lot, which I did. After scoping each others cars out for a minute, he told me he had been looking for someone with a supercharged cobalt and pulled out a GM stage 2 belt which he saws he bought from zzp and a 2.9" pulley. Now like I said I haven't put a great deal of energy into knowing just how much it takes to upgrade to stage two, I mean I always figured I'd buy the whole kit, but since he offered me those two parts for $60, I was just wondering if anyone could help me out with what else I would need to do to run those parts safely. I'm guessing the injectors would have to be changed, probably a tune (which is another issue in itself around here), and would I need to do anything for the cooling system? Anyways sorry for the long write up, and long story short I'm not looking to become an expert over night just wanted first thoughts from you guys if I should go for this or if there is a lot more to it then it may seem like.

Also forgot to mention, my car has an injen cold air intake, 2.5" zzp catback exhaust, and eibach sportlines but I doubt that matters.