IMPORTANT - in a 5th wheel or travel trailers, you nor the dog should be riding in RV while on the road. Most states this is illegible as it is very dangerous.
Carpet can be replace with vinyl, or more carpet. Your carpet layed may not care to tackle an RV. A good carpet person should be able to do the project. Slide out don't make a difference in instalation. In our motorhome, with slides, we replaced carpet. Check out Good Sam's RV web site they have a question and answer section.
PM me if I can help. My husband and I are State Directors for Good Sams in our state.