RCR,
Years back I bought a faded fiberglass boat. I bought a product called Starbrite polish and it worked much the same as waxing your car. The boat came out beautiful. Not sure if it's the proper thing for your HiLo, so if you try it, experiment on an inconspicuous area.
I bought it at a boat dealer but I'm sure I've seen it sold at Wally World, too, and for cheaper. Let us know how it goes.
Bill