Don't know about the YZ80, but have some experience with the ITs:
Most stuff is OK, particularly if you're not after a nut-and-bolt resto. You definitely ought to be able to keep the bike running without butchering it.
IT plastics are probably the biggest hassle, but VMXPlastics are now doing D/E/F guards in IT blue, so that's a help. (The rear guard is actually the shorter YZ style, but it still looks pretty good - I've got a blue YZ125 guard on my IT175F and it looks right, FWIW).
Mechanicals are mostly common to lots of Yamahas, so no drama there.