How do I get a car repair shop to take me seriously?

In early August, I hit part of an 18 wheeler tire. It damaged some thing underneath it and ended up causing my motor blow up. Strange, but true. My insurance covered it, and replaced my motor with a used motor having 60,000 miles on it. I chose the most reputable shop in town to do the work. They had my car for a full month before I got it back. I noticed it sounded loud when I got it back and I felt a miss in it. It also would lurch forward when I hit the gas- as in, taking off faster than I wanted, then abruptly coming almost to a complete stop. I took it back and they said a vacuum line had been loose. It was quieter, but still lurched. I took it back again and talked to the owner of the shop and he acted like I was a moron. I explained it the best I could, even left my car there over night so they could crank it the next morning *when the problem is worse* and they said they couldn't get it to duplicate the problem. They took it to another shop. Since the Check Engine light wasn't on, they had no codes, but they could feel the miss when it was running. Apparently it was luck that they "found the problem." I thought they'd finally fixed it. They replaced the starter and said a bad connection was what caused the problem. It still chugs. We found out after all this that they never changed the spark plugs in the engine they replaced mine with. We changed the spark plugs today and there was oil on them. That's not normal. The shop guaranteed that we would have a good running car after they repaired it and this is just not okay. I don't know what else I can do to get this shop to fix my car RIGHT. I'm sick of taking it up there especially with the owner acting irritated when I repeatedly return. My husband has also been up there and talked to them on the phone. The receptionists and mechanics have all been polite, so I'm hesitant to get irate just to get my point across. The insurance adjuster told me to take the car back up there until they fixed it right, but I've taken back three times already. How do I get them to take this seriously and get my car fixed correctly?