3.8 V6 To A 4.6 V8

ok guys, quick question. how much of a pain in the ass is it to change over my 6 banger to a 4.6 gt. is it the same tranny? what about the wiring and all that, the rear as well. im may be getting into doing that soon. i may have found a motor, but i odont know if its from a late model gt. i have to check it out. so what do i need?

also, where can i get everything i need as. how much does this shit run