Found my dads original 1971 duster!
That is a very healthy attitude. Now its time to get to work. First of all save and print every text conversation with him. Many small things can show intent, even if its trivial. Start a file and put every receipt for payment in there. Copies of bank statements, charge card bills, everything. Establish dates and verbal agreements to the best of your ability to give a timeline that you can back up with documents you have. An attorney will look at your loss and your facts to determine the validity of your case. They will also try to find others who have had trouble with him to establish a pattern of practice. This isn't about revenge, its about compensation for your loss of time and money, and emotional distress. Someone else mentioned having a competent shop look at the car and give a professional opinion of the problems and possibly an estimate to undo the damage. The better your preparation the better the chances for a good outcome.