I also own a 300E and S320. At first glance, they look the same. But the 104 engine on my 300CE has an extra knob on the bottom roll for some type of adjustment.

Here is the link in Flordia, you would have to send in your old module, and they will rebuild it for you. For about $350 extra, I opt to install a new one. One note, they can test your old unit for $50. If I known that, I would not have my car towed to be verified.

http://www.audiabs.com

Jack