I did the plugs on my E320 last October. I also recommend removing the coils since the plugs are difficult enough to get at.
I used the snap-on spark plug remover tool. The number on the handle is SBP 3, but you might want to check out snap-on's web site to verify.
If your plugs have never been removed, expect a fight to get them out. I suggest that you twist the spark plug boot to break them loose and do not pull on the spark plug wire (it may separate from the boot).
I used dielectric grease on the porcelin and the inside boot of the plugs so that they will come out easier next time. I also used high temp anti-seeze compound on the spark plug threads for the same reason.
Expect to bend your hands since the plugs are not very accessable.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles