If u look at the switch, u will notice 2 tiny holes on opposing sides of the switch.

U will need a thin but rigid wire (abt 2mm thk galvanised wire or something like wire clothes hanger, welding rod - u get the idea).

Abt 8 inches long, bend it in half (u-shape). With the key still stuck, insert both ends into the 2 holes and push all the way in until u feel a click. This would release the ignition key switch barrel.

Pull at the key while maintaining "push" on wire and the whole barrel should slide out. Replace the ignition key switch barrel with a new one. Of course, not it means that you have 2 keys, the old one for the doors/trunk and the new one for the ignition. That's how my 190e turned out. No worries.

However, mine is a 1.8 and i didn't have to remove the dash bottom panel. I think on the 2.3, u need to remove the bottom panel first, then proceed as mentioned.

I will scan the diagram of the u-shaped device with it's dimensions (from my Haynes manual) and e-mail it to you soon. Gimme a couple of hours coz it's in the office and now, it is midnight in my home town...

Hang on and prevail!