Changing Front Pads and Rotors
This is not a hard job, really. I just did all 4 corners on my 1986 2.3-16V.
I would suggest you get a Haynes 190E manual at Pep Boys or one of the local parts stores. 84 thru 88, item # 63015, 1990.
There are a couple of semi hard jobs: (1) Getting the caliper bolts unstuck--they are big, like 17 or 19 mm; (2) Getting the old rotor off.
The first job takes as big a wrench as you can get in there to break the old ones loose. If you can get an air wrench in there so much the better. The book says to replace these big bolts with new, because they have encapsulated thread lock. I used the old bolts and used my own permatex blue thread lock. I would have use new ones if there had been a dealer handy on Saturday.
The second job required me to lube up the hub with WD 40 and get under the car with a sledge hammer and pound on the inside edge of the rotor. Just be sure to avoid hitting any suspension members. There is an allen screw in the outside face of the rotor that you must unscrew first.
I would also bleed all of the brake lines and replace with new fluid. I bought Ate Super Blue Racing from MercedesShop. The only thing you have to watch for is when bleeding the rear brakes DON'T LET THE REAR RESERVOIR ON THE MASTER CYLINDER RUN OUT OF FLUID. IT IS A ***** TO FILL IT, BECAUSE IT HAS A VERY HIGH LIP OVER WHICH THE FLUID MUST SPILL FROM THE FRONT RESERVOIR. You may have to jack up the front of the car to get it to flow into the rear reservoir. That part of the job took me a day to figure out what the problem was. Suck out the old fluid before you start (but not all the way) and fill it with the Ate.
You also need to clean and relubricate the caliper guide pins. Also check the bellows on the caliper pistons to be sure that they are not cracked. I had new ones, but did not replace the old ones because they looked so good. I would replace them if they look at all suspect. The caliper pistions have a little ground off shelf on the circular face which must be placed at the correct angle before you reinstall. The book covers this.
If you are not going to detach the calipers from the hydraulic hose, support it from the suspension with a piece of wire.