I hate to say it guys, but you have a long road ahead of you if your trying to collect from the scammer. First of all its a civil case, not criminal. That means that your only option is to sue the guy in small claims court (which you have to pay for). Assuming you build a good case, serve him the papers, and win the case, you are still in the same boat. He will be ordered to pay you back. If he does not pay you back, you will have to go back to court and attempt to collect either his personal property or bank accounts. If he has no money in the bank, and nothing of value in his name, then what? Chances are, he won't show up to court, you get a default judgement, and then you never collect. Not to discourage you, but...
You will be receiving something far more valuable than a refund from this guy. Life experience.... NEVER trust a stranger. NEVER trust a mechanic that you don't know personally. And never never never pay for something upfront.
Sorry this happened to you.