Re: best tools for.....
I used a chisel hand hammer to remove my old floor, was just too scared to use power tools. It's too hard to feel changes of depth, and material thus, you may end up making a cut and find light from under your boat shining through.
Patience is the key I found. You'll find area's that are softer than others, start with those. Don't worry about saving the old floor to use as a pattern, tear it out in pieces, that way you can physically see where you're going, and such.
To make your new floor simply lay out a grid to get your proper dimensions and angles. as obviously your floor will be narrower towards the front.
Once your floor is out, find the center (lengthwise) and run a string (secure using tape) lengthwise down the center. Next take a marker and make a mark on the string every 8". You will then measure from each mark on the string to the side where the edge of your floor needs to be. Record each measurement as they'll all obviously be different. Do this for both sides.
Then take your floor material (plywood) run a chalkline down the center (lengthwise) then mark every 8" on that as well, then simply transfer the measurements and make a mark. From there take a straight edge and connect your measurement marks down the sides. You'll have your floor ready to fit in, simply adjust your cuts as needed to fit in your boat.
I did this and only had to cut one area about 1/4" smaller than what my measurement showed. Any gaps you do have will be small enough that you can fill and/or fiberglass over without a problem.
