I have about 65K miles on my 996 turbo now and the clutch is fine. Make sure you check the rear spoiler. Here are a couple threads that should help:
Pre-Purchase check list... - Rennlist Discussion Forums
996TT Buyer's Guide here on the forum? - Rennlist Discussion Forums
(post#12)
Good luck with your search. A couple of rennlisters are selling their turbos right now. Might be worth checking out.