I don't have my van (and therefore my manuals) handy, but IIRC there was a thread on this recently, and the info for the proper/best gear oil (including synthetics) should certainly be in the archives    ( http://gerry.vanagon.com/cgi-bin/wa.exe?S1=vanagon )in case she doesn't have the link. 

Remove the filler plug first; this in case you can't get it out. If you can't, you can't proceed as you won't be able to refill the thing. If/when you get the plug out, put a large catch pan under the differential pan and begin to turn out the bolts a little bit at a time so that the pan will drop more on one corner than the others. It will probably be necessary to put something like a gasket scraper in there to pop the pan free (do this with the bolts still in place so the pan doesn't just fly off). At this point some of the old gear oil will come out all around; don't worry about it, just try to get most of it to come out in one place and into your catch pan. 
When the pan is off, thoroughly clean the gasket surfaces and surrounding areas and the pan. Check for dirt/debris/metal flakes/fragments. The replacement gasket is quite expensive, so you can either buy one, make your own out of suitable gasket material using the pan as a template or use "The Right Stuff" to seal the pan on replacement. TRS is expensive too, but you get a lot more than one use of course. If you use TRS I strongly suggest you let it sit for several hours or overnight if possible to let it cure. Refill the diff, replace the plug, recycle the old gear oil. 

Cya,
Robert

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Loren Busch
Sent: Friday, June 04, 2010 9:40 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: auto trans final drive

 RE: Lube in the final drive
Annie still hasn't received an answer to her original question:  What lube
(like weight and type) to use in the final drive.  Plus, how/where to drain
old lube?