How do I go about selling my car if I know I'm not going to get as much for it as I still owe on the loan?

I you get 8500 you would take that money and give it straight to the finance company, and you will still have to pay the rest of your loan off. You will need to pay it off immediately so you can give the new buyer the title to the car. If you go the dealership route alot of times they will tack what was left of your old loan into your new cars loan.