Disassemble the hub from the inside out. Remove the gears, springs, etc, as has already been outlined many times. This will leave a white plastic (or nylon) cup in the bottom of the hub bore, which is the back side of the dial.

Then turn the hub over. With a pair of pliers, turn the dial past lock (it does go past the indicator now) till it stops, or about 1/8 to 1/4" past the dot mark. Then either pull the dial out of the with pliers from the outside, or push the white cup through from the inside. You will then see the locking "dogs" on the dial that hold it in(molded into the rear of the dial. You can source replacement o-rings for the dial from a tractor dealership (they can match one by size to be pretty close). Lube the new o-ring with grease, and reverse diassembly.

This makes me appreciate these hubs a lot more. They are really simple to service!