I would say it would take 45mins to 1hour. But may take a little longer if you have a 1.8 as you need to remove some more components to gain access to the starter motor. If you dont have a 1.8 then all you do is
1. Disconnect Battery negative terminal.
2. Apply Handbrake & Jack the front of the car up & Support on Axle Stands
3. Working beneath vehicle, unscrew the nut and disconnect the smallerwire from the solenoid lower terminal.
4. Raise the plastic cover, disconnect the wiring from the larger solenoid terminal, remember the fitting order for use when refitting.
5. Seperate wiring connector incorporated into the main battery lead.
6. Unscrew upper bolts from starter motor.
7. Unscrew lower bolts from starter motor and remove the starter motor.