To remove the brake disk fro the hub, you have to remove the grease cap, loosen the allen screw holding tension on the axel nut, remove the nut, and remove the hub (careful with those bearings and seals if you intend to reuse...I would replace).

With the hub comes the rotor (brake disk). You seperate the two by unscrewing the bolts from the back side of the hub. To ease this job, I HIGHLY recommend some penetrating oil and that you bolt a wheel back onto the hub for leverage.

It's not that bad of a job if you mount the wheel back to the hub.