Go to a machine shop, show them the situation and have them do it for
you.

Not only cheaper in the long run, but it will be fixed right.

Yes, I brought the lower unit to a marine mechanic, and he will give me
a quote in the middle of next week for fixing the
messed-up-threaded-hole (and to remove the propeller that is really
stuck from day one). They are quite busy lately with winterizing and
putting boats in storage. Hopefully, I may be able to get it back in
the next weekend.

Jay Chan