Good advice, although if I could get even half the price of the thing then I'd be tempted to pull it :)

Can any AC shop service such a beast? Do they use commonly available evaporators and dryers? I do have the original manuals and instructions if need be.

John!
Leave that Behr system in there.
Even if it doesn't work.
Just remove the drive belt and ignore it.
The Behr system is still available at a price of nearly $2000.00 (ask Larry
Chase).
They work good when they're serviced and will bring you back additional
money when you sell your van.
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The downside on removing it is that you will probably need an air director
box for under your dash if you remove the system.
Check around for the air box and ductwork before you remove the system. I
just threw away such an air box from an 83 and a non powered vent system
from an 81 (Sorry bout that).