What I'd suggest is when you get an idea of what should be done, shop that work with the idea of getting a better price. I do recommend spending for quality work if there is a shop noted for that. Some places are pretty slapdash.
As for the throttle body cleaning, decarbonizing, and fuel injection cleaning I consider that a repair, not maintenance. A repair is to fix something which is clearly wrong-which in this case would be notable and direct engine performance issues. The FI cleaning, and throttle body would most likely address a rough idle. The decarbonizing would address detonation or ping. These services are not listed in your factory maintenance guide. In many cases these services are sold unnecessarily.
If it were mine if the plugs were rated 100K miles, I'd go that amount. It could take quite a while to run up that mileage in an RV