First of all don't worry about the carpet yet, it will be one of the last things you'll need and some time from now. There are many threads on this subject, try the "Search" thingie in the upper right side of you screen and punch in "floor replacement" or "sole replacement" and take a look. There are a few short cuts, like nailing down a piece of plywood over the old soft stuff and hope for the best, but it's not going to be as long lived a repair as doing it correctly. Lowes/Depot sells an indoor/outdoor carpet that will work in your little Chris. There are also marine supply houses like West Marine and others, that will sell you something similar for twice as much (welcome to the world of boating) Carpet isn't the best thing you can put on the sole (the thing you stand on when in the boat, other then the deck) it has a nasty habit of trapping moisture under it and this can lead to the rot which may be the issue your sole is having. It's likely the plywood has wicked up a bunch of moisture from loose fasteners, cracks, worn out bedding (the goo under cleats and stuff) and rotted out.