http://mb.braingears.com/124_DISC1/Program/Climate/83-556.pdf
http://mb.braingears.com/124_DISC2/Program/Chassis/82-0680.pdf
http://wagoneers.com/DieselBenz/TECH/MISC-INFO/124-series/W124/Index/Misc.htm
Here is the process that I followed since I could not find the instructions on the CD. Note all fastener lengths and locations, they are all different.
1. Remove the arm cover and hex screw from the wiper arm
2. Remove the two rubber strips from each side of the lower windshield by pulling them straight out.
3. Pull off the rubber weather-stripping that runs right across the inner firewall area.
4. Remove the top outer left and right plastic covers. Each are held in place in with two Philips head screws and are also joined to the top inner two covers with white plastic clips. Pull slowly to remove these fragile clips, ask me how I know. Remove the inner four Philips screws holding the inner top two covers down.
5. Remove the 4 screws holding the C shaped rubber grommet which is below the wiper arm mechanism
6. Pull off the engine side firewall weather-stripping.
7. Just below the weather-stripping there are 4 plastic fasteners which hold the sound insulation to the firewall, the inner two have a flower shape while the outer two are flat with two little holes. All four need to be loosened, the outer two will come right off.
8. After step 7 you can pull the insulation forward slightly and find two Phillips screws which hold the center plastic housing down. Remove these two screws.
9. Remove the upper left in right inner plastic covers.
10. The center grate cover should now come straight out.
11. The wiper assy has four 10mm nuts holding it in place, two are on the far right, and one each under the rotating center piece. Remove these nuts carefully and make sure you don't drop them like I did as they can fall into the center black hole which is not accessible. (MIA one hex screw.) I found a similar one holding the A/C pipe on the left side of the inner firewall near the fuse box which I used to replace the lost nut
12. Move the wiper assy to the right, It is not necessary to disconnect the power cable.
13. Remove the outside temp sensor from the blower motor cover.
14. Pry loose with fingers the blower motor harness on the left of the housing.
15. Unclip the 6-8 metal fasteners holding the blower motor cover down, a couple may require a small screw driver, but be careful again. Remove the cover.
16. Unplug the motor, and release the hold down strap using a pointed tool.
17. Oil bearings with ATF. Check brushes.
As in Haynes (reassemble in reverse of above.)