If it isn't obvious, make sure you remove the camera and pan bar from the head first so you aren't dealing with a fragile load.
Unscrew the leveling knob under the head and bowl all the way until it comes off, then lift the head out of the bowl on the legs. There is a large cupped washer between the knob and the bottom of the bowl that provides the friction for leveling the head which can fall free as you remove the knob -- don't lose this.
Be careful when handling the bare head that you don't put sideways pressure on the threaded rod under the head that could bend it -- that could make it a pain to put back together and level it in the future.
