Turn off power to the bathroom fan at the breaker
Remove the fan cover
Remove the fan housing screws or clips
Disconnect the wiring
Disconnect the duct from the old fan
Remove the old fan housing
Compare the new fan to the old opening
Enlarge or adjust the opening if needed
Mount the new fan housing
Reconnect the duct to the new fan
Reconnect the wiring
Secure the fan housing
Install the fan motor and grille
Restore power at the breaker
Test the fan operation