I have worked on the roofs of two travel trailers. One a complete replacement and the other rebuild a water damaged corner along with walls too. In a wood frame trailer the roofs are basically like this. Sheet rubber, plywood or OSB deck, wood joist/truss, insulation, ceiling sheathing. I checked StarCraft web site and there roofs are just like that. When the trailers are built, the walls are installed on the floor deck, then the roof assembly is installed on top of the walls. So what happens is that ceiling sheathing is sandwiched between roof assembly and top of wall. So if you need to replace any of the ceiling system a special procedure is required.
If you only have a leak at skylight, I would assume that caulking at skylight is bad. If it was my trailer I would remove skylight from top along with trim inside. Lift up on rubber membrane a bit to see if wood deck is ruined. You can also push back insulation around opening and see if wood ceiling or truss is damaged. If they appear to be sound, then it is just a matter of reinstalling skylight with new putty tape and Dicore sealant around skylight.
If truss, roof deck or ceiling is bad, then you have a major project on your hands.