What's the problem here, with the A/C and the idling engine?

2000 Ford Contour SE.
1. A/c blows the air out from the defrost vents by the windshield instead of the vents on the panel....

2. When I'm stopped at a red light with car idling, the car starts vibrating as if it wants to shut off. I was told the problem was a sensor that's connected to the engine that keeps the engine revved at a steady pace while it's idle. Is that true?

J J2015-08-03T10:24:23Z

You were told wrong. I'd look for that vacuum leak that is keeping you from changing the vent and it is causing the ruff idle.