Here's a couple of sites to bookmark as a tech reference for the T44 series:
http://members.aol.com/c1j1miller/engine.html#Fuel%20Pump
http://www.sjmautotechnik.com/index.html

Drivers door:
Remove 2 screws in the arm rest.
Remover small screw under the plastic cover in the recess behind the
inside door latch.
Unscrew the door lock button.
Remove small screw in the plastic triangle on the front of the window
and pull off the plastic triangle.
Remove a small screw in the top of the door ends both front and back.
I think this is all of the screws that need removal (been about five
years since I did one of these)
Next pull out at the edges of the door panel to snap it out of the clips
(may take some force).
Once loose lift up to remove from the window opening.
When it is loose take care to detach the wires to the door switches
before they are strained / broken.

Whatever you need to do this for you should also check the wires in the
rubber accordion of the door hinge for broken of shorting. This is a
very common problem area and can lead to a whole list of gremlins.

Not sure of the diff oil but it is important to use the correct one.
Search the history on the AudiWorld T44 forum:
http://forums.audiworld.com/v8/

You should try to get a Bentley shop manual for the car. Check on Ebay.