Labor is a huge factor in maintaining any RV. Labor is very expensive whether you are purchasing it, or whether it is your own. So why waste valuable labor on parts that will not give you maximum performance?
If you use an authorized dealer or a certified Parts and Accessories mechanic to do your work for you, it is a very good idea for you to get as many references from their customers as you can before engaging into any relationship with them. Campgrounds are a very good source of information here, after all, that is where you find owners. And believe me, they are all too willing to steer you in the right direction away from poor service.
If you are that do-it-yourselfer kind of person, then finding quality Parts and Accessories repair parts is your only concern. There are many parts catalogs that feature parts and accessories. Perhaps you live near an supply store and can purchase replacement parts right ovethe counter. A lot of parts such as plumbing parts can be purchased through any plumbing supply store. RV awning parts may be available in your local hardware store. If you own a particular brand name vehicle, then you can purchase Fleetwood parts from your Fleetwood dealership and install them yourself. It has been my experience to shy away from salvage parts. These may be fine if you are buying an trailer part, or a part for you RV door, but for Accessories water heater or gas stove parts, I wouldn't consider anything but new.
I have had success in buying discount parts from flea market dealers or from an parts outlet store. But I did my homework first, and I knew exactly what I was purchasing.
The bottom line is, go with quality service. Even though it cost more up front, it is cheaper in the long run. And do your homework. You have a tremendous investment that you are responsible for. Be good to it and it will be good to you.
Create and Maintenance Checklist for your motor home as you go through the owner's manual. Some things will be done daily, some weekly, monthly, or yearly. Set up a system that will work for you and keep you on track. There are lots of "systems" in an Parts, both inside and out - all the things you find in a typical stick-built house as well as all the things you find in a vehicle - you don't want them to fail due to neglect.
Check the water levels in your battery on a regular basis and add more - distilled water - if needed.
We all have a tendency to accumulate stuff, so here's another important item to put on your maintenance checklist: at least once a year you should weigh your Parts to make sure the load is balanced and that you haven't exceeded the gross vehicle weight rating. This will save both your transmission and your tires.