Ever since I have had my oil changed at my local Nissan dealership, the check engine soon light comes on. Also, my fuel gauge on the dash board fluctuates constantly. They tried resetting the sensors-didn't work. A guy at the dealership said it would probably be my fuel sensors and it would cost around $500 because the engine is a V-6 and it has two gas chambers. He said the car would be fine to drive as long as I watched my mileage with every fill-up. I have been doing this, but now if I don't get it fixed it will not pass the emissions test to get my new tag. I officially got it diagnosed and they said it is the fuel sensors. What questions should I ask BEFORE I give them all that money?