Plug Wires

[sunedog]

99 ML 320 with just over 200K miles. Had local indie change spark plugs and all plug wires at around 110K. I plan to do it myself this time. I plan to get the OEM plugs and wires from Phil.

Do most of you guys replace all 12 wires, or just the ones that are worn out / defective?

And how specifically do you tell if a plug wire is defective. I think you measure resistance, but would appreciate detailed instructions.

Thanks.