Unfortunately, it sounds as though you are going to have to sue them to get your money or the car back. You did not say how much they owed you, but take a look at the limits in small claims court and see if you could sue them there. If so, you will not need to have a lawyer.
I will only assume that you do not have any paperwork on this matter, ie. a contract for the sale of the car, financing agreements, etc. For future reference, you can put right into the agreement what happens if payment is not paid. It does not have to be very complicated, just simple language will do. For this instance, I am afraid that you are going to be stuck suing this guy to get your car back. If and when you do be sure to include all the damages that you listed in your post.
My comments are not intended to establish an attorney-client relationship, are not confidential, and are not intended to constitute legal advice. Proper legal advice can only be given by an attorney who agrees to represent you, who reviews the facts of your specific case, who does not have a conflict of interest preventing the representation, and who is licensed as an attorney in the state where the law applies. less