Tom asks:
> suggestions as to the least stupid strategy to attain this goal?  I 
> merely want some guidelines to assist me when the dealer begins to take 
> full advantage of my ignorance  ;-).  Many thanks.

First off, tell us more:
-- does the compressor run when you turn the AC on (in warm ambient 
temps)
-- if the compressor does run, is it quiet?
-- does the interior fan blow?

You can expect large bills nowadays with any AC work due to tight 
environmental controls exacted on the garages and the very high cost 
of Freon.  The dealer may not even be equipped to service the van for 
AC so you may want to consider a reputable independent certified for 
AC work.

If everything seems 'normal' but the discharge air just doen't get 
cold, you may need only a evacuation and recharge.  Evacuation is 
where they place a strong vacuum on the AC system for a period of 
time to draw out system moisture.  I don't know costs on this but 
expect $80-$120 as a guess.

-dan