To remove the headlight switch you need to reach up under the dash and remove the multi-pin plug on the back of the switch.
Then if you feel around on the switch on the column side you will find a small round button which you must push in. This will allow you to draw the shaft and knob out of the switch.
Then undo the locking ring on the front of the switch and remove it from the dash.
Putting it (or the replacement back is just in reverse.
If you are changing the switch because your lights flick on and offf, it is worth rewiring the headlights through a relay, as this reduces the current passing through the switch.
Steve Wickes, March 2008