1989 23WA Seacraft fuel tank replacemnt/maybe?

[gss036]

Let me start with yesterday. It was the last day (until 7-1-09) for salmon fishing here in our area and I was determined to go. It was windy and 3 ft chop, still fought my way out to the area I wanted to fish, just as I got almost there, my Honda started surging. I knew I was running with only about 25 gallons of fuel and brought along an extra 5 gal container in case my Northstar fuel flow gauge was wrong, as it turned out it was right on the money, said I had 26.5 gallons left, I pulled 26 gallon out of the tank. I had started to season with 75 gallons. Obviously the rough ride really washed the inside of the fuel tank and mixed things up.
A quick check showed that the primer bulbs on the main and Yamaha T9.9 kicker were sucked down flat. Thank goodness I had an extra 3 gal tank for the kicker (carried it for years and never needed until now), disconnected the line from the main tank and hooked that up and fired up the kicker and managed to get back away from the shore line, I had been pushed to within 200 yards of the shoreline by now.
Next step, I checked the SMALL Racor/Honda fuel filter in the motor well and saw that it had a LOT of rust sediment in it. I drained that into the motor well and let it run out the drain hole (no tree hugers around). Re primed the filter and engines and they started for me, possibly averting a disaster or at least was able avert a long slow 13-14 mile ride home. I got back home and spent the afternoon sucking fuel out of the tank. The tank is a 115 gallon factory installed tank. The junk that had managed to plug up the filter continued to flow, but slower since I was using 1/4 hose on the filter, after draining the filter a couple of times, I would guesstimate that I had pulled 1/4 to 1/3 cup of junk out of the tank. Surprisingly, no water was present. I have had a very slight gas odor for some time in the hull, but no leaks.
My question is basically, IS IT TIME TO REPLACE THE 115 gallon tank? If so what is the easiest way to do this? There are 2 deck plates that will come out to give access. How is the tank fixed to the hull? Are they totally foamed in?
I do not need that big of a tank for my usage here in the islands. I am getting really good fuel economy with the new 225 Honda and would only use 20 gallons at most on a day of fishing. Should I go with another aluminum tank or go to a Moeller plastic tank, maybe 75 gallons?
There is a lot of questions here and I apologize for the length of the post. Gary