After looking up on the computer a schematic of the unit, all that was needed was removing four screws to remove the top and side cover which was one piece. Next was removal of electrical connection to burned out lamp, then removing burned out lamp and installing the new lamp and reconnecting electrical connection. Job was complete after reinstalling the cover.
Microwave now working with new lamp lighting when in use.
Continuity checks showed the flame sensor was open. Schematic notes it opens at 217 degrees and closes at 30 degrees. Removed sensor and placed in freezer for twenty minutes. Tested sensor and it was now closed, reinstalled and microwave worked normally. Ordered new sensor in case the original is operating at too low a temperature.
I took the cover off and followed the electric current to see if it got as far as the display. I did not get past the thermostat shut off where the current stoped. I jumped the thermostat and the unit worked. The part was so inexpensive that I decided to replace it rather than try and freeze the old one in hopes of "reseting" it.
