Make sure the timing belt has been changed. Check and make sure the oil has been changed every 3000 miles. Any leaks? Any shaft play in the turbo? Have the caps in the ECU been replaced (or have they leaked?)

I'm having a brain fart right now. I'll post more later. Also, spend a minute or two searching for this kind of question. There have been several threads about this in the last month or so.

Best of luck, and talk him don in price. I don't know off hand, but what is KBB value on the car with that many miles.