83 300D Cruise Control

[rmmagow]

Forgive my ignorance, I'm new to the car and have no owner's manual. How does one activate the cruise control? I've read about the amp thing under the dash and if CC doesn't work I may start there. I probably won't do any thing until I get the full set of shop manuals. If after following directions, the cruise seems to not work, what should be the order of checking for problems?
The Climate Control system. Well, A/C is real cold but on the far right I seem to be missing a button of some sort. The switch has three functions that I can see, a small green colored thing (missing the button), a white plastic switch in the center, about a quarter inch high and lastly a black button with a picture of a fan. It all seems to do something but I can't figure out how it all works together. I don't want to mess with much since I've read the climate control system is a bit failure prone.
The gas pedal. When I press the pedal there seems to be an inordinate amount of free-play. I was checking under the hood and see a lever on top of the valve cover that could well be worn. I'm guessing that the lever actuates something akin to a throttle plate on a gas engined car. Is this lever my source of free-play? Is it an obtainable part? The rest of the linkage seems tight and nicely lubed.

Thanks Much for any advise.