Ordered a new microwave lightbulb and baking element which arrived quickly. Built a stand that was the height of the bottom of the unit, removed the screws holding the unit in the wall and pulled it out on the stand which was on a towel to protect the floor. Rotated the unit, removed the screws holding the top cover in place, release the retention clip for the light bulb and installed the new bulb, replaced the top.
Took off the lower back cover, took a picture of the wiring, unclipped all the wires and connectors, removed the second cover which required bending up some metal tabs. Pulled down the insulation blanket carefully, removed the element retaining plate and pulled out the failed element which was very warped and fractured. Inserted the new element and placed the insulation blanket back in position and then reapplied the inner cover, routing the wires as before, then replaced the lower back cover, reinstalled the oven in the wall. You will need a square drive for the element retention plate.