If you're referring to replacing both rooftops, it should be fairly simple as not much has change in their design. The cutout is 14"X14". You remove inside plastic cover to expose 4 bolts that hold the inside unit up against the outside unit. New units will come with the proper seals, etc. Almost plug-and-play if you have the muscle and basic tool skills. I this what you are talking about?
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie