I bought that 96 Impala off of Ebay, however, I had a lot of contact with the seller and it turned out he was a really good guy. He told me if I didn't like the car when I arrived to buy it he wouldn't hold me to it.
I would just say, read the feedback, contact the seller via the phone, and get a feel for them. I've noticed looking for my GS that I could find a better deal off of Ebay then on. Ebay has gotten so big the deals on cars are not as good as they used to be.