My suggestion for finding a good shop would be to post on the Rennlist boxster, 996 or 997 forum, or on the main 911 forum here on Pelican. Just ask for a recommendation for a shop for a PPI in whatever city the seller's in - lots of local guys who know the good places will reply, most likely. Have the Porsche dealer call them to setup up an appointment and bring the car over, and have the results sent directly to you by the inspection shop by fax or email.
Make sure you've got insurance in place, then you should be good to go! The drive home is the best part
Oh, and make sure you check out the Rennlist Canada forum - lots of local guys there (mostly GTA).