things to look for.

1. ic pump failure. equates to loss of power under wide open throttle. cost to fix at dealer 700$. cost for diy 150$
2. lower control a arm bushings. cost at dealer 700$ cost for parts 80$ and some tools needed (ie: press, spring compressor)
3. seat heater failure cost at dealer approx 700$ for 1 seat cover. common failure diy cost is approx 250$
4. idler pulley failure or grinding. cost at dealer 300 to 350$ . cost of parts approx 150 for all idler(3) pulleys. common issue with mb pullys
5. valve cover breather leaking. cost at dealer approx 100 to 150$. diy cost 10$ for sealant
6. glazed headlight covers, scratches and dents. parts for the xfire are hard to find and very expensive!! make sure the paint is in better than avg condition. also inspect the underside of the bumper for cracks from dragging in dips. bumpers run 600$ or more

i used all my findings at dealer cost to negotiate the price down and then fixed it muself. saved over 4k in repairs and found a great deal!!