I wouldn't sign that. I've been having trouble with the dealership I bought my car from as well. I've ended up hiring a lawyer to get it taken care of. If you still aren't able to get the dealership to be more reasonable, you may try contacting a lawyer. The one I hired is being very reasonable (as I only expect to get the value of new tires on the car - which is around $1,200). The lawyer is helping me on a contingency basis - if I win (and don't win attorney fees) then he will take 30% and if I don't win, I pay nothing except the court fee. At this point I don't even care if I lose a couple of hundred because at this point I just want to prove to the dealership that they aren't allowed to screw people over like they did me.