Bought both replacement parts. Unplugged power. 5 screws will unhinge the bottom hanging panel of the MW. Be careful of the lighting unit also a part of the panel. Motor is removed with one set screw after you unplug its power source. I inspected the Coupler and it was also damaged (stem cracked). I replaced the Coupler first (make sure fitted to proper height for Turning Plate inside MW) then fitted the new motor to the Coupler stem, put new motor back into its holder, returned set screw, and hooked power source back up. Tested the repair.
Might as well pull off the bottom panel and clean it all up since you have gone that far.
Less than 10 minutes excluding scrubbing down the panel.