These cars are pretty low cost in the long run as they are super long life, The problem with a used car can be that the previous owner did not do any maintenance and unloaded his headache to you. just like the rack you experienced, Rack and pinion can wear out on any car and they do cost about the same price, trying pricing a rack for an Accord CL9, or CF3 and you will get your idea.
The ESP malfunction can occur if the mechanic did not pay attention to the column spline alignment which upsets the yaw sensor, you can however reset it and make it learn the new centre position by doing the relearn process. If you see EPS malfunction whilst driving for no obvious reason then there is a 90% chance your brake pedal switch is bad, Its not a regular switch like your jap cars. MB updated the part 2 times now, and the last one is very long life. My W210 also flashed me the error and I ordered the part (approx 15 dollars) and replaced it in 10 minutes - When it really goes bad the transmission will lock in Park and you will be really sorry.
Once its sorted out these cars really show their performance (performance is not speed - its the drive) e.g. the HVAC unit is remarkable if fully automatic, I set mine once and then never have to touch it no matter what the weather, i always have a very comfortable 22C set in the car. After an hours drive you forget that the system was working till you get out the car.
Get under the car and inspect the transmission electrical connector, spin the lock from 11 to 7 o clock and remove the wiring, if you see oil in there you need to replace the connector bushing or at least its O rings (they are not standard O rings btw) or your TCU (EGS in mercedes language) can get soaked in oil and damage itself.
