I would highly recommend replacing both the tumbler and the steering lock. I am speaking from experience here and I cantell you I was an unhappy soul one very hot afternoon in Phoenix in the summer time when the key to my 300D would not turn. After playing with in for about 2 hours, I called the dealership and my local garage and asked the question, "What do you do when your key won't turn in the ignition?" Their reply was "If you try and try and it won't turn, we will take a sawsall and cut it out." I just about had a stroke when they told me all of this plus how much they would charge me for it.

They told me, play with it until you can get it to turn, then do not leave the steering wheel in the position with the wheels straight. If the wheels are straight, the steering wheel will lock. If they are turned either way, the wheel will not lock. Once I finally got it to turn, I went to the local junk yard and bought a used lock. I bought it for about a hundred if I remember correctly and it hasn't given me trouble since.

It is not a hard part to replace. The description in the Haynes manual is pretty accurate if I remember correctly.

Good luck,
Mike

__________________
Don
'85 500SL (Euro) - 186,000 w/a complete restoration and engine rebuild at 154,000
'95 C280 - 174,000