I am currently restoring my 20' Regal and my deck needs to be replaced. I plan to recarpet (used to pull tubes), but I do not know if I should gel coat the deck before I carpet.

Any thoughts?

Gel Coat first.

Really much harder to do it after! SRRY, couldnt resist. Gel it first.

it doesn't have to be gel coat, you can just cover the deck with a coat of fiberglass resin, get a gallon of finishing resin and mix it up and pour it on to cover all your new wood, that will make it water proof and then you can put down your carpet.