1999 Rough Idle Problem

Our Contour with 80,000 miles was running great one minute, then the next began idling rough. It would die without a foot on the gas in neutral.

The dealer just replaced the PCV hose and some idle mechanism (NOT idle air control valve IAC, just can't remember name). They called me today and said the car was running, but still rough. They now want to change the oil as they said it's due anyway and that may be causing it to run rough. They said if that doesn't work, they may have to replace IAC.

My question is are they pulling my leg about the oil change? With the parts they determined and informed me were broken now supposedly fixed (as they explained it), why would an oil change help? The car ran fine before the idle mechanism gave out with the oil that it had, so why the sudden change? My problem is that I don't necessarily trust them, and I'd rather take care of the oil change myself instead of paying out the nose for an oil change! Should I just have the IAC changed?

Thanks!

P.S. - When they pull codes, aren't they specific enough to isolate the problem more readily (ie - code for cam, code for IAC, etc).

changing the oil wont do anything.

its probably the iac.