OMXXX Lifetime CDI engines

Hello, your Benz driver. I’m thinking about getting a C 220 CDI. However, after reading about engine problems here, I’m a bit unsure. My budget only allows a used car, and the diesel models have usually quite good running performance behind them. What experiences have you had? How long do your engines last? How vulnerable is the other mechanics? What does an AT engine (including installation) cost in the worst case? I’m grateful for every information. Martin