Steve,
There are two issues that I can think of if you change your clearance lights (lights high on front and rear cap) over to LED lights. The first and most obvious is to clean the old sealer off very thoroughly and seal the new lights with a good sealer like Lexel instead of silicone. The foam gasket that comes with the lights will leak water into the coach, therefore the sealer is necessary. The next issue is that LED lights are polarity sensitive, and since polarity did not matter with the original incandescent lights , they are not always wired the same from the factory, and you may need to reverse the wires at the light to get the LED lights to work.
Gerald