There should be no drum. I am certain you are talking about front hubs, since that is what wears most of the time. You basically need to remove the caliper and bracket. You can support them to nearby suspension components with wire or equivalent. Then the rotor should come off, it may need some assistance using push bolts or a hammer. The axle nut, and then the four bolts that hold the hub to the knuckle(they come from the rear). Disconnect the sensor and pass the wire through as you remove the hub. This all sounds basic, and there are problems that can occur, the biggest is brought upon by corrosion. If you are in a salty environment, there may be added difficulty to this procedure.