"IF" you end up painting the interior, there is some paint made for the bottom of the hull, ie bilge area's, this might be a better option than exterior paint! You may not have the color options, but it might be a better paint to use, or use a hull paint vs what I am assuming to be typical house style exterior paint. If I am wrong on the type of exterior paint you are thinking of using, oh well! life goes on.
Or do a slight resurface of the hull with new gel coat to smooth it out, then paint with appropriate paint too.
Yes, the work I did to my boat took awhile. The rear took about 20-30 hrs, the head 15-20, main cabin headliner 15 or so, and the front V berth 20-30 too, but that was the first place I fixed, and learned the hard way on some of the things I had to deal with. A bunch of hours needless to say, but I do get a lot of compliments on it, so I am happy with my time spent etc. For your boat it may not be worth it, but for a larger boat in the mid 20 on up range, it could/would be depending upon the boat and model type etc.
She drives me boat,
I drives me dinghy!