First, if you haven't looked and read here
http://mike.focke.googlepages.com/mikesporscheboxsterwebpages
and here ...
http://www.986faq.com/default.asp
you should. It will give you a lot to think about and help you ask the right questions.
I bought essentially the same car recently except it's a 2002 (color/triptronic etc) with 45,000 miles in NM/MT condition. The previous owner met the clinical diagnostic criteria for OCD with this car in terms of service and condition and I paid $13,000.
All other things being equal ... you have Major Maintenance scheduled about every 30K miles. Check to see if/when he did this. That could be costly. It also gives you a general idea of how the car was kept. Also, do not underestimate the high cost of tires on this car. They wear out very quickly. If he just changed them, that's a real bonus. If they have more than 10K on them, you'll likely be looking at new set pretty soon.