Engine power reduced or reduced engine power on dash instrument panel.

Engine power reduced or reduced engine power on dash instrument panel. I had my valve cover gasket replaced yesterday and my mechanic also reset something to do with my gas pedal. Not sure exactly what it was called. Anyways that was yesterday and so today I was on the interstate one mile from where I was headed and suddenly my car started slowing down. It lost power and would not accelerate. The dash instrument panel says engine power reduced or reduced engine power. I know nothing about vehicles but could this have been a result of either of the things that was done to my car yesterday (valve cover Hadley getting changed or resetting something to do with my gas pedal)? Please help me. I turned my car off and tried to restart it but it wouldn’t stay started it died out three times and it wouldn’t go anywhere before I turned the car off. What I’m saying is the car was driving fine on the interstate. All of a sudden the car started like slowing down lost power and the dash said engine power reduced. I turned the car off and then it wouldn’t turn back on or it did it back but it died like three times