Reading through the service manuals for major appliances (furnace, water heater, fridge) is another excellent training tool. They aren't massive and if you look at your own as you review the material, you get hands on correlation with the info. You can also review some of our excellent RVForum Library articles, e.g. Furnace Troubleshooting, RV Battery Choices, Water Heater Troubleshooting, etc.
You also need to be familiar with the use of a VOM (multi-meter) and using it to validate AC & DC circuits, detect shorted electric heat elements, and verify working solenoid relays. You can learn all that online for free.
I agree with the others that you can learn all that here over several months, simply by following the discussions as we help others, but for some people an organized class syllabus works better. Presenting a topic with photos or videos in an organized manner is usually more effective than getting it piecemeal. I wouldn't pay a lot of money for that course, though, simply because there is a lot of ground to cover and 5 days is nowhere near enough to get more than some basics. The $397 price for the home course isn't outrageous, but it isn't a bargain either.
