So I'm knee deep in it now. I'm at the shift cable reassembly stage but
I have to wait for a shift shaft bushing/seal kit because the local
mercruiser dealer is out of stock (typical). There was a lot of
corrosion gunk around the shift arm and shaft so I think the seal was a
bit leaky. It's mostly gone smoothly with only an occasional bad word
spoken. The good news is that the lower unit shifts manually quite
nicely - no binding or stiffness and the prop shaft locks up in the
correct directions. It seems good. My drive shaft splines seem to be in
good shape too and I took the opportunity to lube up the u-joints.

I made the crimp tool for the shift cable boot per the Seloc manual but
I only hot-glued the split nut to my pliers instead of welding and it
worked great! The $20 special socket I bought worked too and seemed to
be necessary. It does seem that outdrive work is meant for people with
MUCH smaller hands than me though.

Does anyone know what the black plastic snap-in insert that came with
the cable kit is for? I haven't seen a similar part on the boat.

Thanks for the inputs everyone. Someday this clinker WILL return to the
water!!