GE overhead microwave EMO4000JWW01 stopped heating. Everything else works fine. Paid $324 in 2005, manufactured in 2004. Any advice on whether to fix or replace? Would like to try to repair first.

You will need to remove it and remove the outer cover,then carefully discharge the high voltage capacitor (an oval silver colored can about 3 inches long) with 2 screw drivers to make sure its discharged,then remove and test it,also there is a high voltage diode that can go bad in this circuit,test this also,there is a small thermistor on the side of the magnetron tube that can be bypassed to test this component,but i would first suspect the high voltage capacitor,the diode,then the thermistor,if all else works i.e. the lights,turntable,etc.