Well, it would be my luck that I would find instructions for removing the inlet AFTER disassembling the unit..! Here is the url...
and, in case the 124 coupes list somehow goes the way of mercedesdot.com, here is the procedure, the original credit for which goes to Ian Read (a member of the 4manics (4-matic) and the Ritter-Easely Lists). Hopefully this will help some other green DIY'er someday:
1. Remove the arm cover and hex screw from the wiper arm [then the wiper arm. Firm pressure and light side-to-side wiggling worked well for me. Also, it comes out easier than it goes in.. -a]
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 holdig 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 old 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. [the flower screws will fit a 7 or 8mm allen head. -a]
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 and 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. [must also remove a retaining clip just forward of the wiper hub. -a]
12. Move the wiper assy to the right, It is not necessary to disconnect the power cable. [clearance here is very tight; the frame prevents movement up and forward, the firewall prevents movement forward and left, and the blower box prevents movement down and right! The method that worked for me was shifting the assembly to the right as much as possible, pushing the firewall forward a bit, and rotating the top of the assembly out of the firewall space. -a]
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 6-8metal 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. [or replace motor! -a]
For future comparison purposes, this job took me about 7 or 8 hours, not including a couple of breaks and an hour detour as I retrieved a mini-screwdriver that had fallen down the water drain. It would have taken less time had I had the above procedure (instead of gingerly prodding and poking the inlet pieces, trying not to break anything) and bought an OE blower instead of aftermarket.
Based on my experience, I would recommend purchasing the OE Behr assembly; it's about 60 bucks more than the aftermarket unit, but you don't have to modify the bracket to fit over the wiring harness, and the stock retaining clip has GOT to be less of a pain to install than the aftermarket clip. The OE unit probably fits more easily under the blower housing too (rotate the aftermarket blower if the cover doesn't install at first).
If the regulator is starting to go, it may be worth it to replace that at the same time - it's literally one extra step to replace, and this is a fair amount of work to repeat anytime soon.
If you lose something down the water drain, either use a magnetic pick-up to try to retrieve it, or use a long something to try to push it out of the drain - which is how i got my screwdriver back!