You both will have one hell of a time getting your plugs out if they are original. Mercedes recommends 100K miles or 4 Years (which ever comes first).

Because you plugs have been in for 6 years they will seem like they are welded in. Take your time and ease each one out.

There is a "special tool" to remove the boot from the spark plug. It is intended to remove the boot from the plug without screwing up the plug wires. What ever you do, do not pull on the metal cable - it will separate from the boot and you will have to replace plug wires.

When I replace my plugs on my 98 E320 I used antiseeze on the plug threads and dielectric grease on the plug boots to make them easier to replace the next time.

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Ray
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles