The pin which holds the adjustable armrest in place has nothing to do with
the adjustment mechanism.  The adjustment mechanism is self contained in
the rest itself and only controls the angle that the rest sits at when
fully lowered.  Something that I'm sure some German engineer got lots of
pats on the back for but now, 15 years later, seems a bit useless to me.
Anyway, I've got some relatively coherent instructions and a few pics for
removal and repair of the vanagon adjustable armrests.  Find them out at
http://www.weidefamily.org/vanagon

Look in the Interior / Interior Bits section at slide 4 where I have two
links for working on armrests.

Brent