Turn off electrical power to the fan circuit at the breaker box.
Lower the grille just far enough to reach the springs that attach the grille to the motor plate. Squeeze the grille springs on each side together and remove the grille.
Verify that no electrical current is present by turning on the pen-type voltage detector and touching it to the wires leading to the fan motor. Do not proceed if voltage is present.
Unplug the fan motor from the receptacle inside the fan housing.
Find the single tab on the motor plate located next to the receptacle. Push up on the motor plate near the motor plate tab while pushing out on the side of the housing. Alternatively, insert a straight-blade screwdriver into the slot in the housing next to motor plate tab and twist the screwdriver. Support the motor plate to prevent it from falling when released.
Remove the nut or nuts attaching the fan motor to the motor plate, using pliers or a small open-end wrench.
Attach the new fan motor to the motor plate using the nut or nuts removed in Step 6. If the new fan motor came with a new blower wheel already installed, the motor plate is ready to be reinstalled. If the new fan motor came without a blower wheel installed, carefully remove the blower wheel from the old fan motor and install it on the new motor. Gently vacuum all dust from the blower wheel and fan housing to lengthen the life and performance of the new motor.
Reinstall the motor plate with the attached motor and blower wheel. Plug in the new motor and reattach the grille.