Hi,
From memory (it's over 12 months since I did the back end), it's 20w50 engine oil in the deDion tube and EP90 hypoid gear oil in the diff.
If you're not familiar with the rear end setup (which I wasn't), my biggest bit of advice would be to get on your back and lie under there for a bit till you're more acquainted with it! All of the workshop manuals give a decent write up on what to check for, but as there's so much to check - UJ's, bushes, bearings, oil seals, a rubber boot, not to mention brakes!! - it's better to know what you're looking at, and then read the manual. Otherwise, it might as well be written in swahili!
I was a bit daunted by the whole thing when I first had to go under there to take the seized calipers off, but I soon got to grips with it. Now I'm lying under Triumphs and thinking how conventional and boring they are by comparison!!
You'll be fine. Enjoy it!
Michael