I replaced a cylinder in an '84 190D in 1999. The part cost $60 and I changed it myself. It was an easy job.
I just ordered a new key for my 300E and I had to go to the dealer and show them my insurance card with my address and VIN number on it along with my driver's license with my picture on it. They made a copy of both.
Apparently, Mercedes has gotten up tight about this business because of a 60 Minute piece about how to steal Mercedes cars.
The dealer told me I had to pick up the key in person. He said Mercedes won't let them ship it or mail it.
Although I do business with Caliber all the time, I recommend going to a local dealership and ordering the cylinder in person. Even if you could fax Caliber the Info they require, they may not be able to send the part to you.