Replaced door. But, before replacing the door, repair company came in to tell me that it wasn't worth fixing, that the replacement was expensive (kinda was at about $200), and that labor to replace would be several hundred dollars. They recommended replacing the unit. I ignored them, bought the door and replaced it. Fixed! Out an extra $100 for misdiagnosis, but otherwise, back in business.
Takeaway: don't slam microwave door--close it gently.