Rotary HVAC

I would like to know how easy it would be to do a complete upgrade of the Silder type HVAC controls to the more recent rotary controls. Over here in old auto componentry dumping ground (yes, Australia), none of the updated look Civics (99-00) got the rotary HVAC controls. Does the heater box need to be changed, or does it just need a different cable. I know most of the buttons are electronic (vent positioning). is the fan control also electric. If most of the buttons are electric then upgrading shouldnt be to hard i suspect.