I have a Hobie 14 of that exact same vintage.
I took the old stripes off with a heat gun.
I filled the cracks with Evercoat All Purpose Filler Formula 27. This stuff cures in under an hour, sands well and last surprisingly well.
Then I sanded the hull. I went from 100 grit dry to 320 grit wet 400 wet then to 800 wet.
There is lots of gel coat on that baby you can sand plenty without worrying about it.
After sanding I polished it up and it looks like new.