Replacing a deck questions?

[cadeco]

Got a Seacraft 20.4 and the deck is soft on each side of the console going to the bow. On the sides there is a channel for the water to go to the scuppers ( self bailing). I have/want to replace the floor but would like to leave that channel the way it is. How that can be done? Should I remove the floor ( let's say about 4 " from it and slide the new under ?) any help will be extremely appreciated. What do you guys think.
By the way: I bought it ( the boat) so i can have something to do on the weekends . I was expecting some thing like that to do( replacing the deck) as well as I'm thinking of closing the transom and installing a bracket. Any ( does not matter how good or bad) opinions will be welcome!