The RV maker is "Mobile Traveller." Chevy is, of course, the maker of the chassis. Mobile Traveller wen out of business some 30 years ago.
I would not worry about getting a manual for the RV as such. Most RV owner's manuals are very generic and don't cover any more information (and very often less) than you can find in something along the lines of an Idiot's Guide to RVs or similar book. Getting a manual for the van chassis should be no trouble if it doesn't come with one, and likewise individual appliances etc. would have manuals available, often online.
Bear in mind you're looking at a vehicle that's over 30 years old. Expect to have some maintenance and repairs to do even if it's in excellent shape, which I think is maybe a bit of a stretch. The brakes may need work from sitting, as might hoses and belts and so forth. Do check the date codes on the tires and see how old they are; driving on old tires is not a wise idea. Check especially to see if there is much or any water damage; that can often be more extensive than it first looks, and a lot of time and/or money to repair properly. See what appliances, etc. work. These are all basic things to check on most any used RV.
