You do not need to remove the casing from the car. You remove the outer covers on each side by popping off the metal clips around the perimiter. There are usually about a dozen, some hiding along the back side. Then remove the clips securing the fan wheels to the motor shaft on both sides. Lift 1 side of the clip and slide to the side. Then you remove the three screws holding the drivers side inner housing, 1 vacuum hose to the rear floor air actuator, and withdraw the housing. You now see the blower motor retaining screws (3) and the resistor. Unplug the red wire for the blower near the switch, cut the black ground wire.(or if you are a contortionist or sadist, unscrew it) and withdraw the motor. You don't have to remove the resistor, but with all the work involved to get in there, I would REPLACE it along with the motor.