There were a couple manuals on the site (see earlier), but they may have been the same one from different sellers. The one I chose provides assembly/disassembly instructions, including which tools are required (even Porsche special tools). Additionally, it has great exploded views and parts lists (descriptions, not part numbers). For somebody used to US customary units and fasteners, having the threads series spec'ed for fasteners I think will be a big help to me. Also, the manual provides torque spec's for everything.
While I haven't tried any procedures yet, they seem to be detailed. In one procedure, it goes so far as to say to heat the transaxle case to 200 deg C before removing the seal (or was it bearing).
The manual covers both C2 and C4. It also covers the entire vehicle, not just the transaxles (includes Tiptronic) if you're interested. The only down side I've found so far is there are places where a page is skipped or missing (say, going from page 34 to page 36).
All in all, I'd give it a thumbs up. I spent $20 USD and to me the exploded views and parts lists alone are worth that (I mean, seriously, when it costs me $15 to fill up my motorcycle these days, what's $20?).
Eric