Following a video guide, I used a cross-head screwdriver to remove 7 screws at the bottom panel. Then I was able to move the bottom panel to access the turntable motor, which was easily replaced by removing two screws and detaching and reattaching an electrical connector. This also enabled me to clean grease residue at the bottom of the microwave, before reattaching the bottom panel.
In addition, the one bottom surface light was easily replaced by unscrewing one screw and moving a bottom light panel down.
Both repairs would be fairly easy for someone with moderate mechanical skill.