Fiberglass Repair Help

From the photos you posted it is hard to tell if the crack is in the gel coat or goes all the way through the laminate. If you are not getting water on the inside it is probably just cracking in the gel coat and not through the laminate itself. If you worked at Boeing in the NDI area you know that Boeing uses prepreg materials for their layups and the resin to cloth ratio is controlled very tightly in the prepegging process. With a wet layup that boats and RV manufactures use there is little control and is pretty much left up to the laminator how much gelcoat to apply. When gelcote is applied too thick which usually happens in tight radius areas shown in you photos, it has a tendency crack in the heat from the sun because of the different rates of thermal expansion between pure resin and the laminate underneath. Pure resin (gelcote) expands much more than the laminate. Looking at the black area the black paint absorbs the heat from the sun much more than the white areas which tends to reflect the suns heat. I imagine the cab sees a lot of movement especially on rough roads which adds to the problem to cause stress cracks in those radius areas. If you are not getting water on the inside I would not do any repairs until after your trip. When you return I would sand the surface cracks off the black areas and paint them white. For the long stress cracks(again if not through the laminate) I would sand that area down to remove the excess resin then go to a marine store and have them mix you a gelcoat to match your color (there are many different shades of white) and screed that over the sanded area just enough to cover the fibers, the thinner the better. I would not drill any holes through the laminate to stop the cracks from spreading the FG cross plys will resist crack propagation,you would only do that in metal and pure resin structures like thermoplastics. Hope this helps and try to enjoy your trip.