How difficult would it be to swap in 4th gen 3.23 disc posi, complete caliper to caliper with e-brake cables to a 3rd gen firebird for someone who doesn't know all that much about mechanics? I wanna get posi and do disc brakes and this would be cheaper and just do it in one shot...

 

I'm doing this as we speak. Ls1 disk, 3.42 posi.
Control arms, panhard, shocks, springs, all bolt up exactly how you take em off the old one. Brake lines, I used the 4th gen lines and mounted my 3rd gen line to the T that bolts to the diff. I've been researching e-brake cables...and honestly I dont know which one I need yet. I'm gonna yank my old one and see how different it is. Also, I'm gonna buy a 1LE proportioning valve...but I think I read that you can get away without changing that.
Do a search, theres a ton of guys who did this, and good info.