Quick fix is to drop the tank, remove sending unit, WEAR Thick Rubber GLOVES and GOGGLES, carefully put in half a gallon of muriatic acid, swish around and spill out. Put in another half gallon swish around and spill out. Wash out with lots of water. The tank will be very clean inside. ream out all hose connections with a stiff wire. Reinstall tank. Install a new inline fuel filter between the tank and pump.
I have managed to save two fuel pumps by carefully lowering the pump end of the pumps in some muriatic acid, then rinse with paint thinner. Carefull not to submerse the electrical components. Note, this will only work if the motor was not power cycled to the point of damaging the electrical components.