Pull the tank and wash it out. I use Super Clean and water. Remove the fuel shut off valve, clean it out or replace it. Get a new tank bushing and reassemble. New hose and filter and you should be good to go.
Engine sounds GOOD, I want one now. Gotta find a decent tractor with a dead engine now.
You may want to start a thread about this project in the CCC/MTD section. This thread gets buried here in the engine section.
951-0171 Fuel Shut Off
751-3008 Fuel Tank Bushing