School-of-hard-knocks ... practical hands-on-training ... and only on demand ... exclusively for personal use. Resources: The Internet and 50 years of wood-woodworking experience, home remodeling, and helping friends. Never been paid for any work I've done, strictly amateur ... but enough experience that I'm not afraid to tackle my own camper.
Repair on my own camper is contingent upon the status of ownership with regards to the age of the camper and if there is any warranty left on the camper. The less warranty, the more I do myself.
The systems on an RV are not rocket science. Simple common logic and a basic understanding of electrical, Plumbing, heating, and air-conditioning, is all it takes.... mostly just common sense. (And a few good Internet sites).