This comes too late for this deal, but I have learned through selling hundreds and hundreds of used cars, trucks, vans, and motorcycles including classics that the deal is going to go down MY WAY. Not their way. That doesn't mean that I won't make some concessions to them to get the deal. But overall, the deal will be done my way and all documents that I have will be executed to my satisfaction. And one document in particular that the buyer has to sign and is all by itself with no fine print is AS-IS NO WARRANTY. A full page that has only that and the vehicle's description on it.

Now recently, Illinois has stepped in and forced a warranty on some used vehicles. That played a role in our deciding to go exclusively to 'rebuilts'. They are exempt from the State's mandate.

There is not much the OP can do at this point except wait for the buyer's next move. As I said before, I certainly would cease all communication with the buyer immediately. Whether the time is right for an attorney is a matter of opinion. It's only money.