<< Your father, as an attorney, should be the first to advise you "Caveat Emptor". You do not have a case. Pay the bill.
You signed a contract, no damage noted. You'll lose this, sorry to say. I can tell by your attitude that you are not one to accept accountablility.
What I see is that you signed off your name, as any in a hurry, less than mature adult did. Now you don't like the consequences, so you want to try and twist the legalities. GROW THE F*CK UP! >>
Give me a break, if you were in the situation of having to pay almost $700 damage, you would bring it to court to. Don't give me that crap that it wouldn't happen to you because you would have inspected the car before accepting responsibility for it blah blah blah, because people do things when they are in a hurry and if you say you don't or haven't then you are a liar. Anyone who would just pay for this without a fight would be the one who needs to grow up and get some balls.