Do you have any proof as to your transaction? If not even in small claims court it will be hard to prove. Your word against his.
This has happened to me regarding work I've performed for plumbing, and in my opinion it's not worth the hassle. And it does sound like you're on your way to a degree from the University.
Proof is what I am worried about. I think i screwed myself. I listed this lift kit on C-list for 300.00 dollars plus stock parts to put my truck back to stock. He gave me 200.00 cash the day we traded the lift for the stock parts. He sent me a text message saying he can give me the other 100.00 the next day when he got paid. I called him back and said ok. The next day he got sent to west Texas for work and was gone for a week. He called me and said when he got back he would pay me. The next week when I heard nothing I called. Phone was no longer working. I have gone to his house 3 times and found someone home once. The person said he was gone with his girlfriend and did not know when they would be back. The little moron could have been in there for all I know. His truck with my lift is sitting at the house. It has bald tires and no inspection, so it just sits there. So here is the only proof I would have:
1. My c-list ad stating what was for sale and how much.
2. His reply saying he wants it.
3. His text saying he will give me the other 100.00 later
4. I also think I still have all the reciepts from when i purchased the lift kit origianlly
5. Pictures of my truck with the lift kit on it.
I would like to talk with a lawyer before I waste my time to see if I even have enough proof.