I had the samething happen to me several months ago. The car lot agreed to fix the car for me, they actually offered! They told me that if I wanted, I could skip the next payment or two and it would not cause any problems. They would add the cost of the repair to my overall bill. I flat refused to skip the payments just because of what you are going through. I was so scared that I would not get my car back. I knew that as long as I was still paying them and paying them on time, there was nothing they could do.
I hope everything works out for you and sorry about the bad luck.