When I changed mine, the new one was one piece and the old one came out in two pieces. You could see where the casting broke on the old one. I changed it out after finding it during a search for the cause of an intermittent SRS light.

There are plenty of nightmare stories of keys stuck in broken tumblers so it would be prudent to go ahead and get a new set from Mercedes. You can get a generic tumbler for less but then you'll have two different keys for the car.

glenmore
1991 300CE
2000 C280
1990 LS400