How Bad Am I Screwed? :(

I would clean it off good w/ gasoline and alcohol and install the switch w/ epoxy. The switch will probably last forever. Next time you rebuild the tranny you can consider the helicoil or bushing fix.

Good luck finding a helicoil that works. The switch has a fine thread, which is rare. Even for common threads, helicoils require a special tap which is expensive. I once found that a standard metric tap was identical (or close) to the special tap needed. Was I lucky or are all their "special taps" actually standard ones and they don't volunteer that information?