Ok, the plug has been repaired.
With the threads stripped from the previous plug, I was able to take the 1/2" drill bit and run it in the hole by hand; took out very little, if any material! Covered the end of the tap with bearing grease and carefully started it in the hole.
Once it bottomed out, I backed it out and noted a good bit of debris on the tap. Then I took several Q-tips, dipped in grease, and swabbed out more bits. Once I felt that I had all the bits cleaned out, I stuck the red nozzle of a can of carb cleaner up in the hole, past the debris, and emptied about 1/2 the can in there to backflush the hole.
I then took the new plug and installed it; I *think* it must be an oversized one (didn't say that on the package!) because it basically retapped the hole. I would turn it in a couple of turns, back it out and go some more.
I cleaned the hole again as above and ran the plug back in. I left the plug out for now to allow the carb cleaner to dry.
I think the repair will be ok. Threads look pretty good. I'll use a rubber washer and go easy on the torque.