Overhauling the engine is not a big job. Remove the tin and the radiator. Label all electrical connections. Remove the engine from the tractor. Pull the head and oil pan. Check the wear of the cylinders by measuring the ridge and the cylinder. Try for no more than .0010 wear. Remove the pistons and rods being careful not to nick or damage the crankshaft, label and ensure all pcs go back in exactly the same place. I use surgical tubing on the rod bolts to ensure they don't nick the crank. Cut the ridge (ridge cutter) and break the glaze on the cylinder walls (use a hone if you have one, 400 grit sandpaper if you don't. Try for a nice crosshatch pattern at about 45 degrees.) Before assembly, wash the cylinder walls with ATF (automatic transmission fluid) until clean. Look carefully at the old rings as you take them off. Rings have bevels or unique edges that clearly indicate the installation patterns. Clean the ring grooves with a piece of an old ring, removing all carbon. If you have a ring expander, use it to install new rings, if not, carefully spiral the new rings on to the piston. Torque all bolts in sequence and carefully, twice. Use a decent torque wrench. You will not be disappointed. Anyone that is careful and pays attention can overhaul a motor.
Tom