Where are you located? You could also try to find a used unit on
Car-Part.com--Used Auto Parts Market. I do believe we have a few tranny gurus on the forum here. I'm not sure if they do work on 996 P cars, but try posting a thread in the 911 tech section here:
Porsche 911 Technical Forum - Pelican Parts Technical BBS and see if anyone can direct you to a Pelican forum member that does rebuilds.
If you need help with the removal of it or anything else be sure to check out our articles for the 996 transmission here:
Porsche 911 (1998-2012) Technical Articles - Porsche 996 & Porsche 997 - Pelican Parts.