Sorry to jump in...but the Mercedes specific oil filters have a check valve that stops the oil from coming back down. This might be your problem there.
Also if the stick shifter for the 300e is the same as the automatic then you might have to get under the car to remove the handle on top of the tranny it does not screw of from the top. Thats how it is on the automatic.
Hopefully Larry will get back to you if I didn't get any of this right