Not to make an excuse for a shop that did not inform you
of this but they *all* will develop a leak over time.  The case
material is aluminum and the drain plug is steel.  You run
a steel plug into aluminum threads and no matter how
careful you are they will strip over just a few times.  The
proper way to fix (and what they should have had straight
from VW) is a Time-Sert threaded steel insert.  Also, you
must use the aluminum crush ring for the drain plug that is
specifically for the Vanagon and not the copper ones for
the steel pans of the Golfs/Jettas.  It got to the point that
while I was working as a VW dealer tech that I hated to
see a Vanagon in for an oil change because sure as John
Anderson dropped his trans into reverse instead of drive
they would leak afterwards.   Poor design by VW- IMO.
~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~
Todd Hill
VolksWerks Transaxles
Olympia, WA