Re: foam
Check-out the restoration section of this site. There are numerous discussions re: if you should replace the foam or not. I feel that the general consensus is that in our style of boat, the foam is not structural, therefore is not necessary under normal use... HOWEVER... if you should ever swamp your boat or have a hull breech, then the foam could save your boat from going to the bottom. Many have replaced the foam with the pink or blue insulation boards from Lowes or Home Depot. Others have used pool noodles, and I think a few may have used soda bottles.
I put foam back in mine, mainly for sound deadening vs floatation. Keep in mind, it's not the foam that helps your boat float in normal circumstances. In fact, adding the foam actually causes the boat to sit lower in the water, ever so slightly. 100 lbs of foam weighs the same as a 100 lb person/ weight/ fuel tank etc.