Drive the mower onto a level surface and disengage the blade control switch.
Move the motion control levers outward to the neutral lock position, set the parking brake, stop the engine and remove the ignition key.
Use the foot pedal to lower the mower deck to the 3 inch height of cut mark. Allow all moving parts to stop before climbing off the mower.
Remove the belt covers over the outside spindles on both sides of the deck by removing the securing screws with a nut driver.
Undo the two screws on the front outer edges of the floor pan with the nut driver. Lift the front of the pan and pull it out to access the belt drive mechanism and idler pulley.
Take a snapshot of the belt layout with a camera phone or digital camera in case you need to refer to it later.
Hook the tip of the spring removal tool provided with the mower into the outer end of the spring between the front of the idler pulley pivoting arm and the securing hook attached to the deck. Stretch the spring sideways just enough to unhook the end from the securing hook; doing so will facilitate removal by easing belt tension.
Strip out the worn belt and route the new belt around the engine pulley, idler pulley and mower pulleys. Ensure that the belt is properly seated in the pulley grooves and reattach the idler pulley spring.
Reinstall the belt covers over the outside spindles and replace the floor pan.