Avi ♥ Tekserve
A happy ending to the MacBook saga.
I ended up getting in touch with Jay from Tekserve, who was sympathetic to my plight and offered their help in getting the screws out. I dropped by and within ten minutes, they told me that they had extracted the screws, so I had them replace the top case while they were in there. Apparently their techs didn't even blink. Amazing.
It took them a little while to find the part, but now I'm home experiencing the happiness of a warm MacBook. Thanks, guys!
As an unrelated aside, while waiting there for help on Monday I saw some Mac G4 Cube cases used as Kleenex dispensers. I thought that was just for display until I saw a tech have to tell a woman that her hard drive failed. Kids, remember: backup, backup, backup! Time Machine is free. Use it.