I just changed the front brake pads and rotors on my Sisters 2002 C240. The degree of difficulty was about the same as my full size GM cars (which I have done several times)
1. Start by sucking half of the brake fluid out of the master cylinder reservoir, and replace the cap..
2. On my Sisters car, the rotors were worn enough to warrant replacement, and this is what I did. ( I'm not sure, but I have been told that Mercedes recommends rotor replacement when replacing pads).
3. Very important! Place the car on jack stands. The job will require pulling and tugging on tight bolts that could pull the car off a jack.
4. Remove the front wheels and the rotor retaining bolt, This is a Torx T30 bolt that will require a Torx tool to remove. Do not remove the old rotor yet.
5. Unplug the pad wear sensor connector (this is on the right wheel only)
6. Remove the two 12MM bolts holding the wheel cylinder assembly and remove the assembly. Use a piece of wire to hold the assembly so it doesn't hang by the brake hose.
7. Remove the two 18MM bolts holding the sub assembly to the wheel spindle assembly. (These bolts may be very tight ).
8. Remove the rotor. (On my sisters car, I had to use a two pound hammer and whack the rotor very hard to dislodge it).
9. Use a large C-clamp to push the wheel piston back into the bore. (this will force brake fluid back into the master cylinder, (lowering the level on the master cylinder in step #1 will prevent the master cylinder from over flowing and making a mess).
10. Snap out the old pads. the inside pad and the outside pad are not the same, so match up the new pads with the old pads.
11. Remove the brake wear sensor from the right pad. It pulls straight out of the pad. I reused the old sensor in the new brakes. If your old brakes are badly worn, you may have to replace the sensor (about $10 at NAPA)
12. Push the sensor into the new pad, and slide the pads into the wheel cylinder assembly.
13. Reassemble the components that you removed. Use lock-tight when replacing the bolts and make them very tight. Don't forget to plug in the ware sensor connector
14. Top off the master cylinder with DOT4 brake fluid.
15. Test drive the car, and have a beer, your job is complete. The total time took me about four hours.
Note: I bought the rotors and pads the the local NAPA dealer. They sell two grades of rotors and two grades of pads. I bought their best quality (more concerned about noise than stopping ability) The total cost was $222.74 with the AAA discount. My sisters regular Mercedes shop quoted a price of about $700.