there are basically two problems: (1) the tumbler in the key wears out and (2) the column lock wears out. If you have the key assembly out, it's and easy fix to remove the column lock pin and spring as per the instructions on this site. If your tumbler is worn out, as mine was, you can get a new tumbler at your dealership, just bring in the housing and they will look it up for you They will tell you it won't work because it needs the electronic chip, but buy it anyway, it's around $70. It comes with a micky mouse blank key which is nothing more than a guide to cut new keys with. I bought a new folding key like the original with the housing. I then had my local key shop take the chip out of my old housing and put it in the new housing and cut the key to match the new tumbler. It, much to the dismay of the Mercedes Part Dept, works perfectly. Note, these chips have the program burnt into them and can not be reset. You could set a new chip to your car's serial number which stays the same if you only replace the tumbler.

Removing that column lock pin and spring, just makes sense; you will never miss it and I doubt if any column lock has ever saved a car from being stolen.

Hope this helps.

Dave