Can someone tell me if the spark plug replacement is a DIY procedure and how long should it take? Also, Should I replace the wires as part of the replacement( I don't have a problem with them now)?

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Jerry DC
99 E430 "Stock"

Budget 3 hours. It's a DIY. You just need to be "gelenkig", have the right plug cap puller (I used a 19mm box-end wrench), and be patient. You might need a slight spray of silicone lubricant or similar to help push the plug boot back on, since you can't get much leverage. Also, use anti-sieze on the plug threads.
You also need a Torx bit to remove the coils from the valve covers. Of course you will need the right spark plug socket, and a torque wrench.
To gain access on the passenger side, remove the air filter box, MAF sensor and the intake tube.

Some folks swear by the OEM plugs, but I'm currently running Bosch plus 2's with no problems. I don't know of any reason to preventively change the plug cables.

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Prost!

thanks

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Jerry DC
99 E430 "Stock"