Here's my two bits on sliding doors:

The sliding door mechanism was not working well in my '81, so I tried to oil
it.  The owners manual points to one spot on the link pin that should be
periodically lubricated.  That helped some, but the real problem was with a
broken hinge link spring.  This is a big sucker about 4-5 inches long that
pushes the back end of the door out so it clears rear quarter panel and then
can slide backwards.  When it was broken I needed to push the rear part of
the door out after releasing the front latch.  This was easier from the
inside than the outside. 

To fix it I had to take the door off (heavy for one person, but possible)
and remove the interior panel.  Mine was broken at a cast metal connector
that connected the spring to the hinge link.  The cast metal peice must have
just cracked in half and the spring was totally disconnected.  I got the
part number from the fiche (thanks Joel), and the dealer had this small
piece (actually two matching pieces) for about $5 each.  It was pretty
simple to put back together.  By the way, the local junkyark wanted about
$75 for the whole assembly!

        I noticed at the Pfeiffer picnic that the Copleys' bus had the same
problem.  Some DPO had attached an extra handle to the outside of the door
at the rear to make it easy to open. Their rear hinge assembly was also
broken, but in a different spot.  Another cast metal piece, the one threaded
inside the spring was snapped.  I guess these metal pieces are a little
brittle, eh?

Is this a common problem with these doors?  

John