...and for 15k you should be able to get a fairly nice Boxster with a good history. I had all the same concerns a few years ago when I bought my '00S. I did as much homework as I could and bought one anyway. I did get mine from a P-Dealer. I probably paid a little more than I would have from an individual, but it came with 4 pages of maint. work they had done on it and a year wtty. (which I used)
Not sure on finding a roller but here would be a good place to start.
http://www.oklahomaforeign.com/
good luck!
sean