You could use either epoxy or polyester resin to patch it up and add a little glass cloth where you need to reinforce it. If you use epoxy, don't use plyester resin over the epoxy. Just make sure you sand any smooth surfaces before using resin since it may have wax mold release. As far as gel coat, I'd forget it. It's very hard to do and not worth it. Fair it and sand it best you can and spray paint or brush paint it to make it look nice. Let the resin cure good, before you paint. Use oil base paint.

It's really if you want to make it seaworthy or like new.