Very simple repair. Just shut off the water to the house, drain the water line, remove the 2 retaining clips, and pull out the shutoff valve. Have a towel ready because there will be some water running out of the valve that could not drain. Remove the turbine support/housing from the water output side from the softener by pulling it out with your fingers. Simply slide off the old turbine and replace it with the new one. To reassemble, simply reverse the procedure.
Be careful not to snap the water valve retaining clips when removing them and reinstalling them.