ooo, not recommended, not by me atleast
trust me, the iPhone is COMPLEX frm the inside, i remember, when it first came out, and i wantd2hardware unlock it, the earlier firmware obviously, i was like "woah" when i opennd it up, and i've opennd up everything i can gt my hands on mind u :P umm, if u have ur mind set on having a new one, then u can open it up and try, tht way, u wont have ANY regrets if u even mess it up... but u cnt mess it up more anyway... i hope im making sense..
abt the prices of the spare parts, i have NO idea where u wud find them