On my 98 E320 I just twisted the neck 1/2 turn to get it off. If you look carefully at the base of the neck there is a plastic tab that must be "unlatched" for the neck to turn. It will also give you an indication which direction to turn the neck (I can't remember if it is clockwise or counter clockwise). I replaced mine due to an oil leak as well. No oil leak since.

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