I am only familar with the E320's - not sure if this was a problem with the E430's.
To remove the harmonic balancer you will need a metric hex head "socket". I bought a set of three at an autoparts store. One size fits the rear differential plug and the largest size (don't recall the exact size) fits the harmonic balancer.
I used a 3/8" x 3" socket extension to keep the flywheel from rotating. The prefered method is to rent the proper tool (try a local rental store which rents automotive tools).
As Kestas mentions a breaker bar is essential. I tried an air impact wrench but at the time I did not have a suitable air compressor to break the bolt loose.
When replacing the harmonic balancer, put some blue locktite on the bolt to keep it from coming loose.
1998 Mercedes E320, 200K Miles
2001 Acura 3.2TL, 178K Miles
1992 Chevy Astro, 205K Miles