That was an easy fix. I have had several fifth wheels in the past years with fireplaces. Two of them have failed due to a short in the hot wire inside the fireplace. It is an easy fix if you are careful. Remove the fireplace and remove all the screws from the back of the unit. It is unplugged of course. Follow the power wire into the unit and more than likely the white wire will be burnt and falling apart. Pull enough slack to trim back all the burnt and hard wire and crimp the wires back together with a new connector. Be careful putting the back cover on because the screws will easily strip out. Don't use a screw gun! Also be sure to check the other connections while the back is off.
