help with 4000q?

[C1J1Miller@aol.com]

My '86 4000csq (175k mi) has needed a bunch of repairs in the last year, and
has a couple remaining problems I need help/advice with.

Repairs completed this year include:  collision repair, drivers front corner
(frame machine, no paint, new marker light...), new alternator, replaced
large seal in rear diff., both front wheel bearings, new backup switch, new
(used) rear calipers, pads and rotors, tune-up (plugs, rotor, cap, cleaned
air filter), new Leistritz muffler and gaskets (cat back).  Car has a noisy
fuel pump and old fuel filter, but the lines are too rusted to change the
filter etc. without replacing the lines as well.

Current problem:  car has a squeel when decellerating in gear (no throttle),
and sometimes when engaging clutch.  Car also has a vibration that I can't
cure by balancing tires (several times), etc.  Vibration lately seems like a
shudder at around 25 mph, with or without the car in gear.  I get a steering
wheel vibration (worse at around 65 mph).  Subframe bushings seem good (per
mechanic).

The mechanic says the center bearing in the driveshaft is making the noise
(some old grease is sprayed on the tunnel by the grease fitting).  We added
some more grease to the fitting, and the noise (may?) have subsided a bit.
 He also says the vibration is caused by bad motor mounts and mounts for the
rear diff.  The car was up on a lift, and there was a lot of play in the
motor mount (drivers side below the brake master cylinder), as well as in
both side differential mounts.  He says it may also be the cause of the bad
center bearing in the diff.

Question:  how hard is it to replace the diff mounts and engine mounts?  I
would like to try this myself. 

Second question:  the mechanic says Audi only replaces driveshafts.  What is
the WMB part number that works?  How hard is it to replace yourself?  The
shop wants over $300 and that's only a rough estimate.  Would I do better by
going to a local WMB shop (not dealer)?

Thanks for any advice....
BTW - I've been saying I'm going to sell the car for several years and 75k
miles...this time I may do it, if I can afford the upgrade to 200qw or the
like...