PI Intake and Head swap

Wassup fam.. I am purchasing a PI Intake and Heads(for $600) from a friend that swapped his out of his 2002 GT. He is giving me the whole setup including the tb, stock plenum, fuel injectors and rails. Now I don't need the tb and plenum since I have replaced them with aftermarket parts. My question is this. How much of a job is it to swap out the heads? I won't be needing to modify the intake gasket and stuff since I have the heads. Is this something I can do myself of should I take it to the pro's? Also what kind of gains should I expect from this swap? Thanx guys..

Yeah I spoke with another friend and he said I should definitely have the pro's do it. I was leaning that way also because I want to have it dyno-tuned and have the ecu flashed while it's there.