i use the same technique with the plier as haasman.
no need to buy expensive tools.
once you identify the faulty resistor-it can be removed from the spark plug wire by unscrewing it in the counterclockwise direction.
the resistance of the resistor should be 1000 ohms or 1kohm.
the procedure for unscrewing the resistor applies to wires made by bosch or beru as far as i am aware.

you can buy the resistors on their own from the fastlane where you can also see pictures of the resistors.