On my own boat I've been doing cosmetic gelcoat repairs
to stress cracks and small delaminations. I've learned to match the existing gelcoat but it is a painstaking task. If it is not perfect the repair will show up like a sore thumb. For a large area, I believe your best bet is to bite the bullet and repaint. One part paints are easiest but two part paints will last longer. I suggest you do a bit of research
to decide which you have the skill and/or patience to do. No matter which, it will be the prep work that will make or break the job. The fellow on the boat next to mine did no prep work besides wiping down with acetone and then applied a one part paint using, of all things, a disposable nylon chip brush. From 50 ft it looks pretty good, but when you are within about 15 ft you can see the brush marks and the runs.
For the non-skid I've used Awlgrip with sand but it is now very expensive. Soon I will be re-painting my own non-skid and will try using Kiwi-Grip, a water
based paint that has had some really good reviews
. I bought a quart along with the special roller that gives it the non-skid texture. If it turns out alright, I'll buy another gallon or so to finish the boat.