Remove the front plate of the dishwasher and locate the thermostat. If the thermostat is not located in the front of the unit pull the dishwasher out and remove the back access panel.
Disconnect any wires or other parts that are in the way. Separate the wires with a flat blade screwdriver carefully to keep the wires from breaking.
Take out the screws attaching the thermostat to the firewall and remove it from the dishwasher. Verify the replacement part matches the original, including the wire connector.
Place the new thermostat into place and secure it with the screws. Connect the wires and replace any parts or cables. Attach the front or back plate and replace any molding.
Run a hot water cycle and verify the water is heating and the cycle is able to complete. Check the drying cycle and prepare the first load of dishes.