Need Help! Electrical Problem w/Gearbox

Hey there, wondering if anyone else has had problems with their gearbox. I was at the grocery store this evening and I couldn't get my car to start. Once I had it started 20 minutes later, I couldn't shift into P or R. I felt like a moron because I had driven into my spot and actually had to mount a snowbank so that when I threw the shifter into N it would move my car backwards enough to get me out of my parking spot. In a panic, I called my Mercedes dealership and they said that I should have my car towed to the dealership on Monday (they were 1/2 hour from closing and I was about 40 minutes away from them). They when I got home -- I COULDN'T REMOVE MY KEY!!!! Needless to say that I'm not a happy camper. I then again called my dealer (I have his cellphone number) and he said for me to giggle and shake the shifter a few times to try and get the shifter into the P position. To no avail. I tried for 1/2 hr. until I just gave up. Its kinda cold outside (minus 10C is not temperature that you want to be sitting in). I'm a bit peeved as it seems Mercedes knows of this potential problem. I just want to know how to remove my key from the ignition so that no one steals my car before I can get it towed to the dealership on Monday. HELP PLEASE and Thank you!