Car Dealership says we MUST re-sign our contract

We leased a car in Jan. Three weeks later we get a call from the dealership that GMAC kicked back the lease because the dealership claimed more rebate money on the original lease contract than they were allowed to=it was the dealerships mistake. They made out a new contract,and are insiting we sign it, or
return the car. I told them I would return the car. Which we already registered. I am so upset about the poor customer service on this, that I truly don't want the car anymore. The payments end up being the same
so the dealership said we are committed to sign. They said they will sue us if we return the car. GMAC does not even acknowledge the contract=when I call they have no record of us in their system yet. We have not made any payments except the initial one at the lease signing. The dealership said we can pay them when we sign the new contract, which by the way will be dated the same as the initial contract in Jan, even though it is now almost March. Our "trade in" has already been sold off by the dealership and we received notice from the bank that the loan was pd in full, so there is no way we can get our old car back. Do they have legal grounds if we don't sign, and return the car? We live in Nevada?

Take it easy. Why do you want to get yourself all upset? If there is a simple mistake and you did nothing wrong, and won't be hurt, what do you have to gain?