Removal and Installation of a headshok is quite simple, actually seems to simple for a fairly complex shock. To remove the shock, remove the stem and plastic dust cap or dial on top of the shock to begin with. Next get a piece of wood and a hammer, high tech tools at work here! You need to support the frame as sturdy as possible for this. Next you just hammer the shock out of the frame using the block of wood on top of the shock tube.
Installing the HeadShok requires a little more that removing one did. When installing you have to keep the top bearing of the headset from coming out as you drive the shock back into place with a hammer. A pipe the same size as the bearing is needed to accomplish this (Cannondale actually sells a tool for this, it's just an aluminum cylinder). PVC, or some soft metal would be the best choice for this application.