Turn off power to the bathroom fan at the breaker
Verify the power is off with a non-contact voltage tester
Remove the fan grille
Remove the fan housing cover if present
Disconnect the wiring from the old fan
Disconnect the duct from the fan housing
Remove screws or fasteners securing the old fan
Take out the old fan housing
Compare the new fan to the old opening and duct size
Install the new fan housing
Secure the housing to the framing
Reconnect the duct to the new fan
Reconnect the electrical wiring
Attach the fan motor assembly if separate
Install the fan grille
Restore power at the breaker
Test the fan operation
Check for proper airflow and unusual noise
Seal any gaps around the housing if needed