I would keep looking, personally. It sounds like you are getting $6500 in exchange for an $8300 vehicle. Plus, people who modify their cars like he did tend to drive them hard, further decreasing their value and reliability.

If you were just paying $5500 for the car, it would be a decent deal. But selling your Durango for $8300, and having almost $3000 sound in your pocket after you purchase a car sounds like a better deal.