Tips on Buying Cars: obligation, buyers remorse, money change

Question
I just signed a number of documents agreeing to buy a truck. There is a trade involved and I plan to pay the remainder in cash (check). I don't have the truck, they don't have any money. I am pretty certain that I will go through with the deal, but I am having "buyers remorse" due to the fact that I am trading a perfectly good (paid for) truck. Could I just say I am not interested any more?

Answer
I'm not a lawyer, and I don't know if this still applies, but I do remember this from my old business law classes:

A contract for more than $500 must have money change hands for it to be binding.  If you gave them no money, then it's my understanding that whatever you signed is not enforceable, which means they can't force you to go through with the deal.  But I would run this by an attorney or legal expert (legal secretary or your state's attorney general office, maybe?) before relying strictly on my advice.