The major difference between all the DIY-er types (like me) who have been RVing for decades and fixing their own rigs, and an RV tech with decades of experience, is the tech has seen EVERY brand of RV and appliance out there. They have detailed knowledge of how different manufacturers do the same things, chronic issues, recalls, best practices, etc. They know why things break, and how to fix them so they stay fixed.
A guy who has worked on RVs for a living, 8 hours a day for years, has a breadth of experience much greater than the rest of us, who fix our own stuff if it breaks, or might help a friend with an RV problem.
I'm happy to have these guys posting here, and grateful that they freely share their expertise and experience.