Re: dry rot problem
Any part that is discolored should be cut out and around 8 cm more. There are several products that kill dry rot. Any form of Copper Napthenate does it, one trade name is Cuprinol. Common salt will also work. Mix up a stiff solution and soak the wood thouroughly. You will have to keep salt on the wood to keep the dry rot from coming back as the spores are unbelievably tough. There are some new forms of wetable epoxy resin that not only encapsulates the spores and rot but gives adequate strength to continue using the wood. I have no personal knowledge of this stuff though. Some here will chime in on its effectiveness.
$3K is a bunch of replacement. What would it be if you did it yourself? Okeuma (sp) is readily available down there. I imagine the cost should be reasonable.
I know of one little 16 foot workboat that the deck is replaced every three years like clockwork because the owner is chemical sensitive. It costs less than $250 American in materials to do it right now. When I replaced the deck on my MFG Gypsie I actually used plywood from packing crates that were scheduled to be a landfill problem. It took me almost a day to do the job. All I needed was a portable saw a power screwdrive and a staple gun.
I am particularly lazy, so you can get by with manual tools.
Reuse your fasteners or order some good stainless steel or silicon bronze ones from a good chandler. If it is a salt water boat don't use brass screws as the zinc will leach out quickly and leave very weak fasteners.