Disconnect the battery.
Remove the steering wheel.
Remove the instrument panel.
Remove the center console.
Remove the glove box.
Remove the heater controls.
Remove the radio.
Remove the air vents.
Remove the screws holding the dash in place.
Pull the dash out of the vehicle.
Now you can remove the blend door and replace it with a new one.
To reassemble the dash, follow the steps in reverse order.
