Just get a PPI done by a reputable shop and go on that. I had a PPI done on a car by this shop in Manhattan Beach:
http://www.bimrs.org/profiles/AutoWerkstatt.html
Based on his inspection, I passed on the car. Good guy, nice guy, slightly expensive, recommended by my local indy, Vanguard Motors here in SF.
I think you'll generally have good luck with mechanics you find via the bimrs.org website.