Replacement of the headband pad is not a trivial matter. You'll need a small soldering iron, a #0 Phillips screwdriver, and several hours (the first time).
Start by removing the back cover of the right can and unsoldering the wires (make note of which goes where.
Next is the horseshoe shaped cover on the inside of the hanger assembly. Just pry it up gently and evenly. The cable just lifts out.
To removing the hanger assy from the bracket on the end of the headband, you have to pry off the two caps on the ends of the bracket and remove all the stuff in there. Remove the cover over the spring and ball (don't lose them) then the two support bushings. As you remove the hanger, you'll find the detent plate for the ball. Just slide the hanger off the wire. At this point, make note of how much cable is free - during reassembly you'll want to check to make sure you don't have too much or too little.
To remove the bracket, position it in mid travel. Remove the screw on the inside, then slide the inner cover up about 1" and pull the wire through. At this time, also remove the two inner pieces from both ends of the headband pad (the outer pieces will just slide down towards the ends of each bracket). The R bracket can now be removed from the end of the headband (the slide is the lock piece that keeps the bracket from pulling out in use.
Finally the plastic piece at the end of the headband can be removed, along with the headband padding. Note the routing of the cable so you can put it back the way it was.
Reassembly is just the reverse, of course with new padding.