You'll need to remove the entire vacuum cover in order to replace the switch, and you'll need to pop off the actuator as well.  You'll be able to gently pry it off the two lugs that it sits on.  Once you have that off too, you'll need go to the underside and release the switch with a small flat blade screw driver by pressing down on the tension clamps (not sure what to call them) on each of the four corners.  Press the switch through to the outside.  You can then use some needle nose pliers to pull out the spade connectors and reinsert them on the new switch.  Snap the new switch back into its place, along with the actuator.  Also, be sure to install the switch in the right direction.  Otherwise, high will become low and low will be come high when you press the actuator!