I wouldn't worry much yet about how to fix it. I would worry about two related questions "is the dealer going to pay for the repair?" and "do I yet own the car?". If the dealer is going to fix it - let them worry about it. If they're not going to fix it I'd be checking state laws in your state - mandatory used car warranty periods, purchase cooling off periods, etc. It could be a simple repair and it could be an expensive repair.