electrical shuts off - while driving! no brakes no steering

I own a 2002 E320 4Matic that I bought new in 2002. It has around 118,000 miles on it. I am a single mom and have always kept it maintenanced. On May 5th in the AM while driving my teen to school (going 42 MPH) the electrical shut off. No warning, no lights, nothing. It had never happened before. My brakes dod not work not did the power steering. We almost wrecked. I took the car to an authorized MB service company and they ran all sort of diagnostics for about 30-45 minutes and could find nothing wrong so they replaced a few older parts with Mercedes new parts to see if that would solve the issue. Three days ago driving home with my 12 year old we were turning a corner and the electric stopped without warning or lights and brakes stopped working as did steering which resulted us getting into a head on crash with a semi truck in my neighborhood. We were going 10 MPH so I was a little banged up but ok. My son luckily was not hurt. The airbags did not deploy but this could have been tragic. I am beyond livid. I do not care if it was 12 years old, my child could have been killed. My teen could have been driving. I had just come off a road where the speed limit was 45 MPH. Very bad situation. A car like a Benz should not just turn off like that without warning. And it never shows any issues popping up. My car was totaled. This is not something normal that should happen. My car is in USAA's lot know for adjuster. I let them know as well what happened.