Yes - the title is correct and it's a long story why... but I didn't realize the latches on the door were plastic (non-conductive) until about 2 seconds AFTER the big flash of light and the breaker on the main panel tripping.
The fix fro the microwave was simple - 2 screws at the top of the vent part along the top, 1 screw to remove the clip holding the keypad, and 2 screws to open up the service bay. Then the main fuse it right there - pulled it and it failed a multimeter test.
Ordered this fuse, came in 1.5 days - installed it - now cups of old later afternoon leftover coffee can be made hot again!