Just found this link. It offers some great pictures on replacement of the plug. One should be aware that new data plugs (MB calls it a pilot bushing) now come complete with BLACK o-rings (white ones have been superceded) and are available from the dealer or online for around $7.00. P/N is 203-540-02-53.
http://www.installuniversity.com/mb/w203/w203/trans_oring.html