Sometimes the check engine light comes on and nothing is wrong with the car. For example, if you don't tighten enough the gas cap after refueling, the light comes on and after a few driving cycles, the light is off again.
I guess you will never know if you got ripped off or not. I hope not. I suggest next time something wrong with your car, you first submit the problem to CEG forums. With the members experience, you'll most probably find the answer before going to the garage.
Welcome to CEG and good luck.
