One possibility that no one is considered:

Maybe the van DOES still need the head job, and maybe Jack simply patched
it up with chewing gum in order to screw yet another person for $3500!

By the way, I think that I would have agreed on the price before letting
someone tow my van across the state.  Basically, he was holding it hostage
then and could steal it from you for peanuts because you already implicitly
"owe him" for the towing.

Michael