it will look like this.
Mine leaked right through the terminal and I replaced both pumps, filter, accumulator and the hoses except for the one I couldn't get loose at the tank.
Your mechanic does not seem too familiar with MB's, because you are right, the filter is between the pumps.
I try to find a picture of the EHA, which I believe is the black box leaking under the hood. They also have a habit of leaking.