You are getting good answers and answering your own question.
My take on it:
1. No one but yourself left to work on it.
2. Sounds like a whole bunch of work, possibly.
"It's a very complicated set-up to do correctly."3. Sounds like you may NOT fix it and it may still leak after awhile.
4.
If it operates quietly and does not leak too much, leave it alone! wait awhile and see how much it bothers you and how nice the new ratio is.
5. If those have been known to leak, others have had to find and fix all kinds of causes.... It ain't the differential for me.
6. Switch it someday. Original is sometimes not worth saving. The more modern diffs do not have any problems like that at all!!!! and every shop in NorCal will work on them.
7. You could find out, after much work and expense, that this yay-hoo damaged something bad and he knows it. He may have tried the "Permatex/Loc Tite fixes" already. That's why he is being an axehole now.
"Showkey: He replaced some of the studs, and said that the new ones were not very tight. (I asked him why he kept going???)". What if it's unfixable? Then you are dead in the driveway!
8. Buy a drip pan.
9. After being on Stovebolt for 11 years, one thing I've learned is that if I ever buy an AD I will convert to open driveshaft and associated differential in a New York minute.
10. Don't forget there is a critical break-in procedure for your diff. Follow it. Peace.
http://www.differentials.com/technical-help/ring-pinion-gear-break-procedure
