Engine repair service near Duluth, GA

The oil plug fell out of my car while I was driving, and my engine needed to be rebuilt due to the damage that it sustained. Tim was the worst mechanic that I have ever worked with. He originally told me that it would take about a week and cost me around $2,500, and he ended up having my car for 5-6 weeks and charging me $3,800. I'm not blaming him for the increased cost and extra time, because I understand how those things go. However, when I started questioning some of his extra charges, like $800 for a machine shop that he allegedly had to take parts to, he refused to show me a receipt (which he is legally not obligated to do), and then got very defensive and started bullying me. I never said I wouldn't pay him, but he told me that I had to pay in either cash or a money order because he didn't trust that my check wouldn't bounce, even though I had already paid him over $2,000 in checks that cleared without a problem. He threatened to sue me several times and called me an immature child, all because I wanted to see a receipt for the machine shop. Before we started having our disagreements, Tim kept telling me how he appreciated my trust, and I now believe that he appreciated it so much because he saw it as an opportunity to take advantage of me. He even went so far as to ask me what my credit score was, and then propositioned me to co-sign a business loan with him. I thought that was extremely unprofessional. Personal problems aside, my car ran perfectly before Tim did work on it. Since I got it back, I have had problems with the transmission skipping, as well as with the electrical system. When I informed him of the transmission problem, he was defensive again and claimed that it had nothing to do with the work he did. I would never let Tim work on my car again, and I would advise everyone I know to avoid utilizing his services as well. I am very disappointed with this business and mechanic.