Hi,
What Mr. Sunshine says it correct.
1) You will be surprised to know that the service dept. and sales dep't don't know each other. Sometimes they are actually a separate company. Once you buy, the salesman is useless. Many service departments. will only work on RVs bought at that dealership. Or tell you they can get to it in 3 months.
2) Unlike cars, RVs aren't covered by lemon laws.
3) Make sure to hire an independent experienced RV mechanic to examine the RV you are interested in buying. A couple hundred spent now can save you lots more after you buy the RV and have driven 2 blocks.
Check out this website
RV Service Reviews for reputable RV Mechanics.