When it comes to refurbing it, Bob Morrison has done some good articles with pics that should help. When I bought my Lightweight, the dealer did all that crap for me. Have fun and good luck.
I get 30-35mpg out of my 1997 tdi D1. I think that's pretty good for a 2 ton lump of metal with a 2495cc diesel engine, and the aerodynamics of a housebrick. Just drive her nicely, and she'll be nice back. Probably.
I once had a replacement stub axle where the thread had not been cut along it enough. It would tighten right up, but I still had play. Caused some head scratching.
You should be able to get it done between 9 and 3pm. Or between 3 and 6pm. Its not a hugely complicated job. Look for threads on here, or Mr Haynes book.
Really, I think you're better off with soundproof matting, carpet, good rubber mats and no leaks. Oh, and decent door seals. Hmmmm, maybe a bit much for a Landy
I'm betting that somebody breaking a D1 will let you have the soundproofing matting for a few quid. As for stable matting, it can be quite inflexible, so see it first if you go down that road