Engine stalls

I went to Aamco to bring in my SUV because my service stabili-trak came on with my check engine light. It came on after I came home from work but my car worked fine before that light came on. The next day when I left for work when my car is sitting at the light it started to shake then sitting it cut off with the car still in drive. I had to turn off my engine and put it in park then turn it back on and it started back up. But still when idling it shakes. I took it up to Autozone so they can read the code. It said misfire in cylinder six. I had my mechanic look at it and switched the coil that was three and six I believe. After that the code did not say that anymore like three others came on one said a map sensor. After he switched them back the car would not start now it was saying no oil pressure. When the car sat at the first click you can here the fuel pump start I think he said. The dash said low engine power as well. I took it up to Aamco basically saying it was a oil pressure switch so they supposedly fixed it $364.00. Later it ran for two days now it will not stay started the engine starts, but shuts off and it smells like gas on the inside. After listening to this guy saying your car is still going to misfire because you need a tune up spark plugs. So I changed them the car is still misfiring I already put new coils on as well. My mechanic cannot figure out what is wrong. I am looking online can you help me please?