I'm trying to determine how to access the fresh water tank and potentially replace the sender to the gauge that displays how much water is left in the fresh water tank. The manual shows the 32 gal fresh water tank in the center of the stern of the boat. If I try to get access via the floor hatch (where I can see the bilge area, it appears it is fiber glassed over. Do I need to remove the fish box on the helm and access the tank from the Top? Will the sender be visible on the top of the tank? Is the tank made of fiberglass or aluminum? Thx