Installation:

1: Install this mod:
https://www.gta5-mods.com/vehicles/coach-rv-add-on 

2: Install Menyoo if you have not already done so:
https://www.gta5-mods.com/scripts/menyoo-pc-sp 

3: Extract the "Furnished Galaxy Roamer.xml" file to "E:\SteamLibrary\steamapps\common\Grand Theft Auto V\menyooStuff\Vehicle"