I belong to Passport America and have stayed at Nashville Yogi Bear Campground on Music Valley Drive for half price. Passport America subscription $44 ... 2 nights at $62 discount, you have more than paid for your 1 yr fee. Enjoy the rest of the year...
In March my preference would be Grand Canyon South Rim (North Rim area isn't open til mid May) and then Sedona and Red Rock Canyon area including several of the National Monuments devoted to the cultural heritage of the area.
On any used RV I would hire a mechanic and a mobile rv repair person to check it over. I would want to know the good, the bad, and the ugly of such a vehicle BEFORE I purchased. I have heard and read too many tales of people trusting the dealer only...