Typically, RV owner's manuals (from the RV maker themselves) are very generic, covering many different models, and not very helpful. There are a number of beginner's guide to RVing sort of books around that cover the same sorts of information at least as well.
As was said, if you want chassis or appliance information, that is fairly readily available. If you're looking for electrical or plumbing diagrams, they may very well not exist, or at least not be available to the general public.