I had one of my Roadtrek marker lights go out, so I decided to replace the three amber ones with three LED amber lights.
They come in two pieces, a base, and a sealed lens that houses the led lights. Just remove the old lens, and base, and replace with the new ones. The new base piece looks identical to the old one, but the new lens didn't want to snap into the old base, so I replaced the whole unit. I suggest you save the old screws, because the ones that come with the new lights are two small for the mounting holes in the roof. Make sure to re-seal the hole, where the wires go through, with some clear silicone.
I think they are a little brighter than the old ones, and with them lasting a 100,000 hours, they shouldn’t have to be replaced again.
I purchased the lights from Optronics Inc. They can also be orderd with the standard bulb.