I'd want to see the details, but I can say from experience that the 1 year Good Sam service plan I purchased was pretty much worthless. Everything that is likely to happen (or did happen) is excluded. Granted, most major systems are covered for catastrophic failure. Thankfully, I didn't have to put that to the test.
My wife and I have discussed purchasing a follow-on plan from one of the better-rated providers, but have decided not to. The cost/benefit ratio is simply upside down. I'd like to have the peace of mind, but the cost is just too high for the value provided. We'll take the approach that "things happen", and we'll pony-up to fix them when they do. We expect the overall cost over the life of the coach will be less than the cost of the Service Plan.
In our favor, our coach is newish (2014) so the power train is covered by Ford for two more years. The E350/Triton V10 is damn near bulletproof. If there are no problems by then there aren't likely to be any time soon. I can do most non-chassis related repairs myself (and have done so far). For us it feels like an acceptable risk. The calculus may be different for others!
Please do note - you called it a 5-year Extended Warranty. It is not. It is a 5-year service plan. The consumer protections that apply to true manufacturers' warranties do not apply. The distinction can be significant!
If you do buy a plan I would look at an "Exclusionary Plan". These are plans where everything
is covered except what is specifically excluded. You know exactly what is and is not covered. If it isn't explicitly mentioned it IS covered. Most plans, including Good Sam's, are inclusionary. They only cover what is explicitly stated. What you think is covered may or may not be - lots of room for interpretation.