190 16v alternator removal replacement
I just did this job, thought I'd leave this message for those that do searches.
First of all, remove the covers (metal heat shield and plastic cover) before the two bolts holding the alternator in.
Second, loosen the top bolt. Then, get under the car to access the bottom bolt. You actually unscrew the nut that is towards the rear of the car to get this one out. I had to get under the car, but i think its possible to do it from above.
Third, remove the wires, spray them with electrical cleaner. I had to move a piece of wire (ground?) from the old unit to the re-built one, but yours may differ.
Fourth, take the two bolts out, lower the alternator down through the engine compartment to the floor.
Fifth, do everything in reverse. Good luck =)