I have a fiberglass boat with a mist/flake paint, and it is beginning to look severely sun-damaged. Is there anything I can do to reverse this process? Will it have to be repainted? :'(

If it is surface oxidation, you can use a rubbing compound and a buffer to remove it.  3m makes good products,, and they even have a marine application.  I got mine at academy.  you can get their auto grade compounds at oreillys.

and no, i do not work for 3m.