Does anyone know where one can find literature on the maintenance and/or the
installation of a VW gas heater?  I recently obtained one, but do not know
how to install it.  I have a 1970 camper. 

My Bus has two holes (appx. 1 inch diameter) in the firewall to the left of
the fan shroud.  Are these holes used for anything related to the gas
heater?  My Bus used to have a gas heater installed in it. 

And also, How much are the gas heaters worth (in working condition)?
The previous owner of my camper kept the gas heater because he felt it was
worth something, presumably more than the 500 bucks I gave to him for the
van, spare engine, spare transaxle, 5 spare tires with rims, and assorted
parts.  He wouldn't even show it to me, because I wanted it thrown in with
all the other stuff. 

Wolf

1970 Bus in Albany, NY