Fuses And Circuit Breaker problems of the 2004 Ford Mustang

I have manual transmission. When you put it in reverse it would not go backward. I took it to the dealer, when I got the car back, second gear grinded very badly. I did not have this problem when I initially took the car in. They kept telling me to drive the car and it would work, it way out. It did not work its way out, and I took it back in for repairs. They had the car 9 days. After I picked the car up, a few days later I realized the reverse lights were not working, I took it back to the dealer and they said it was a fuse . A few weeks later I realized it was out again, they again said it was a fuse, and they said it was not working because of my aftermarket radio. I decided to just drop the car off in the dealers after hour drop box to make them look at it because of the reverse lights not working. It turns out the circuit breaker and switch were broken and had to be replaced. I just received the car back today and now the "check engine" light is on. I noticed this before I even got out of the dealer's lot. The check engine light was not on when I turned the car in. I turned the car around and the dealer told me they were to busy and could not take the car back so I do not know why the check engine light is on. All of these complaints are in regards to the transmission. I have no idea what the check engine light is from because they will not take the car in until Sunday.