You can find manuals on the different house systems by going through the manufacturers; i.e. Dometic for your reefer, Suburban or Atwood for you W/H and so on. When you figure out what engine and chassis you have, there will be manuals out there for both of them.
What will be hard to find is things like wiring and plumbing diagrams, but because of the number of years and owners intervening since manufacture, those aren't as useful as you might originally think.
Set up a search on ebay for literature on your rig, and ebay will email you any time a new auction comes up that matches your search descriptions.
Also, google "manuals Vogue diesel pusher" and you'll find at least one poster on IRV2 that had a 1983 Vogue with a full set of manuals. Always worth a personal message or two.
Life rocks when your house rolls
Senior Chief & the Cheese Queen