"New" 300D

That is your idle increase knob. Turn it to raise the idle when you 1st start the engine cold.

Turn the headlamps on, then pull the knob out 1 click.

Try turning your emergency flashers on and off a few times. Then try the turn signals.

I do not believe he is has a USA car because we do not have the idle increase knobs after 1980. The idle increase became part of the injection pump in 1981.

I believe the knob is the idle speed adjustment.

Fog lights activated by turning on and pulling out the light switch.

1. What do I need to know about the little idle knob on the dash to the left of the steering wheel?

That's your manual choke.

1. Is there a separate switch somewhere for the yellow driving lamps?

The fog lamps are lit by first turning on the headlightS and then pulling on the dial

1. Will I ever get the turn signals to work?

The blinkers are controlled by the hazard flasher on the center console. This is removed by gently prying it out. (I used a butter knife). And you'll choke when you find out the cost of this little gizmo.

Toblin

Talk to striplin at mbz.org, he'll sell you a good used working one cheap.