And yeah, I got it back together. But by the time it was done, it was probably a good thing that the kids were in bed.
Bought a replacement gear assembly off a Milwaukee parts supplier for $40US. One wee spring was missing, but I got it figured out.
You can avoid this entirely by NOT trying to drill through 2′ x 3″ rectangular steel tube with a 4″ hole saw. Apparently this is too much.
The upside, the replacement part has been upgraded in the areas that failed.