tenbear,
Yes, that's possible but you have to find and change every "item" connection in the entire RV that's wired wrong and even then it doesn't truely correct the wrongly wired issue that exists. It's merely a quick bandaid type fix of the known and found wrongly wired items. What's still looming?
If just changing the wires at the fixtures, it would be wise to put a piece of red elec tape aroung the positive wire so down the road you or anyone who buys your RV later will know which is the positive wire for sure. Why not do it right??? Then you will have piece of mind also!