hello guys,
thank you for all your replies.
here is the story.

i have also called the other dealership and they told me that they don't drain TC as well. I took the print-out from the post earlier and my work book (bentley publishers) where it clearly says about draining TC and went to the dealership. Right away i called the service manager and was ready to argue. But, they he was so extremely nice, he took me to the shop and there was several mechanics (older guys, looked like they knew what they were talking about). And we started discussion. One of them explained the reasons for not draining the TC because there is a pump right before the TC, so if you'll drain the fluid from there, after starting-up car the TC wouldn't be filled-up and you'll get some 'metal-on-metal' action. But i did show them all the manuals and how it should be done. They said that they'll do it but it would be first time ever they'll do it on 300e. As i said, they were extremely nice and friendly. I though for a while and decided that if it works fine right now, and they have never done it in their lives, i would just leave it like it is and change it myself in the summer. The only thing i'm pissed off at myself that i spend 150$ for nothing...lesson learned.