Ross, welcome to iRV2. Check out the Vintage RV Owners Forum here and introduce yourself. Lots of good advice here.
As for manuals and parts, the chassis is a regular Ford E350 chassis with the normal engine and transmission. The appliance, heater, frig, stove, A/C and furnace are all standard components that you can get some manuals online and most RV stores can get you the parts for them.
If you have some specific questions, post it in the Vintage or the general motorhome forums.
The Tioga is owned by Fleetwood and you may be able to get some electrical diagrams and such from them.
Amateur Radio Operator (KE5DFR)|Full-Time! - 2012 6.7L Ford Crew Cab Dually -2013 HitchHiker Champagne 38RLRSB - Travel with one Standard Schnauzer and one small Timneh African Gray Parrot