The first item on your to-do list should be finding and stopping the water leak.
Next is remediating any damage. I suspect the roof covering must be removed far back enough find solid wood sheeting. Most likely any roof insulation in the area is also wet and must be replaced. If you are lucky, that will be the extent of damage.
After removing all wet materials, the trailer must be allowed to thoroughly dry before beginning any repairs. I would use a mold/mildew treatment like Concrobium Mild Control
( there are other brands too) after everything is dry.
Repair/replacement of damaged stuff is next. After you have everything finished, Hopefully you can find an RV repair shop that has, and utilizes a SealTech
machine to locate any leaks in your trailer. This system really does find any leaks, then the technician seals them.
Yes, the outer skin is aluminum.