Spider web cracks are just cosmetic cracks in the gel coat. A good shop that repairs
fiberglass boats could grind out the cracked gel coat and re gel coat that area. Color match and cost would be my concern here. Old oxidized gel coat could be hard to color match. If you choose to repaint the whole trailer. the cracked gel goat would have to be removed and the area repaired before
painting or the cracks will just "telegraph" thru the new
paint. I'm not sure where you are in your trailer reconditioning process so you might consider making this decision one of the last in the reconditioning process. The cracks are unlikely to get worse and they are not structural.
If you decide to do a paint job, preparation is a huge part of the job. All
windows, hatches, vents etc. need to be removed and all surfaces sanded. If the gel coat is oxidized and faded,
painting would be the best option.
Me, unless it's really bad, I would just go camping and work on other trailer projects.