We've driven over the highest mountain passes in the West with two gas Class A's and a gas Class C. We wouldn't win any races, but I wouldn't worry about that issue.
Excellent post by DrewE. Great idea to rent an RV locally for a short trip. In addition to the things already mentioned for you to think about, I always look at the accessibility of the utility hookups (dumping the tanks, etc.) and storage bays. Some of those sewer hookups on the RVs seem very difficult for my body to access without hurting my back! Actually I sometimes sit on a stool to deal with my hookups on the motorhome side.
