Well, the idle air control
(sorry i said air idle control earlier) valve is an electric "valve" that keeps the throttle open enough for the engine to idle. Without this, the engine would, as you have experienced, die without you pressing the gas. This is the problem correct?
see this thread.
this is a drawing of it. Over time they get clogged with crap and dirt and lose their ability to open and close. (high idle and low/dying).
The oil pressure gauge, i wouldnt really worry about. Its not a necessity, many newer cars now a days don't even come with an oil pressure gauge.
If you feel the need to make this gauge operate properly, it's most likely the oil pressure sending unit, which sends the electric version of your oil pressure to your gauges.
This is ~$50 from the dealer. You want to buy this part from the dealer because many after market ones from autozone or advanced tend to go kaput after a short time, or even run backwards. Heck, it may even be a loose wire that's your culprit.