Good luck on the manual search, but a couple of points: Most RV manuals are full of generalities but little specific detail. They'll tell you how to clean your seat belts, but don't tell you where wires or plumbing runs or fuse locations. I'd suggest going through the RV and noting make and model number of every installed item. Then Google them with the word "manual" appended on the make and model. Most appliances and systems will have manuals available to download.
You could also go to other manufacturer's websites and read manuals for other RVs. They will give you behaviors to use when setting yours up at a campsite, loading, storage hints, etc.
Here's some resources:
Service Documents and Manuals
Manuals - 1989 & older - RVing-The Midwest Connection
Manuals - 1990 & Newer - RVing-The Midwest Connection