The air sample for the HVAC is mounted to the passenger side knee panel, remove the hose and plug
Now the left side.
12) Sitting in the driver's seat, pull the instrument cluster toward you. It is a friction fit, usually can be pulled out with finger pressure out to both sides, rocking from side-to-side. If you have a stubborn one, ... you might benefit from a set of M-B dash removal tools, I haven't needed them yet.
Once the cluster is out far enough to reach your left hand behind it, unscrew the retaining ring on the speedometer cable (directly behind the center of the speedometer). I have not had a problem with a 124 having too little cable for this (yet).
Unplug the wires from the cluster, should be plenty of cable. If the wire numbers are no longer on the warning lights you might want to mark them before removing them. The rest of the wires will only plug into one place, only one of each connector. Unplug all of the lights and wires.
If you are in an '87, the temp-display wires are pigtails, they unplug in the middle of the wiring under the dash, three separate plugs.
the cluster removed
13) Remove the left speaker grille and 8mm bolt beneath using steps 1-4 as a guide.
14) Remove the left vent similar to step 9.
14.5) Reach into the opening and un-plug the speaker wires same as RH side.
15) Pull the headlamp switch knob off. Might take some rocking as you pull, some take a strong set of fingers.
16) Using the slip-joint pliars (best tool for this, honest) loosen the nut from the headlamp switch and remove it.
17) CAREFULLY pry the headlamp switch bezel toward you. It will also remove one end of the brow over the steering column. Carefully pry the mating trim from the dash on the other side of the steering column.
Here you can see the nut behind the knob. It is easily removed with channel locks or by hand if you have removed it before