The one time I was going to buy a used car from a dealer, I insisted on taking it to a mechanic I trusted to have it checked out at my expense. The dealer fought it hard, but I insisted, and found some interesting things.
1. There had been a fire under the hood, which had been repaired and repainted. This wasn't a problem, but it was good to know.
2. The brakes were not legal for sale in California due to excessive wear, and they had falsified the records (either to hide the problem, or because they never checked).
I *highly* recommend having your own mechanic take a look at it. You won't regret it.