I am not familiar with your fifthwheel, but I would think you have an inverter/charger.
I assume you want to just add solar and not do a total system upgrade. One of the nice things about solar is the system can be upgraded very easily as depending on needs.
A general consensus in sizing the panel array is 100 watts of solar for each 100 amp hours of storage capacity.
There are not many solar dealers that have experience with setting up an rv system. two that I am aware of are; www.amsolar.com
These two have the most experience that I am aware of.
You will probably be getting quite a few responses and everyons has different needs and systems.