>  The front
> stabilizer bar is not attached at the ends. It is there and mounted
> to the frame but not attached to the front suspension. How big a
> problem is this?

Depends on how much high speed driving you plan to do around curves.
Some 4WD guys disconnect them to give the front wheels a greater
degree of independent travel over rough terrain. This comes at the
cost of increased "sway" on the road. No "problem" per se, but it
ought to be set whichever way suits your needs best.

>
> How do I check whether the 4wd is functioning properly?  What to look
> for in terms of problems?

All you ever wanted to know (and more) about testing the
Vicious...err..VISCOUS Coupling:
<http://syncro.org/VCTest.html>

> There is a vertical "canister" in front of the drivers side rear
> wheel. What is this?

AC receiver/dryer? That wouldn't be Syncro specific though. Might be
the fuel filter, as the Syncro fuel tank is wedged in above the
transmission..

>
> What is the round knob on the dash under the 4 wheel line drawing?
>

Rear differential lock knob. Pull to lock your rear wheels--- if it's working.

> Is there a web site that deals with syncro issues?
>
<Syncro.org>

You'll also definitely want to join the yahoo syncro vanagon group/list.

> Oh yes, what is the value of something like this. No visable rust,
> 250 000 Km.

To me, it seems like price is "pretty much whatever the seller can get
away with". I'd have to defer to others on that. Unless it's been
modified from stock, in which case we know it's worth $6,000!

--
John Bange
'90 Vanagon - "Geldsauger"