Re: 1921 Conn Alto needs complete overhaul...
I belive that conn may have special nub screws that maybe deserve a reading up on, dont know for sure as I've never worked on one.
I would clean the crud of the tonehole rims, but really, there's no way I know of to deal with an unlevel tonehole rim other than painstakingly conditioning pads to match the contour as best as you can.
Other than that, don't lose parts, try to keep track of what screw went were, and if you're so inclined, used a gentle polish like Haggerty's.
[not a pro. Just an amature repair person]