Replacing floor and want to add a swim deck

[garlicbreath]

I just bought my first boat, and noticed the floor is soft in spots. I am pretty mechanically inclined, and have a full shop of tools, but limited woodworking tools. Mainly my 18V dewalt setup.
What does it entail to replace the floor?
Do I need special wood?
And how about some links to home built swim decks? I have all the metal working supplies to make any type of frame needed.