it runs very rough when idling but at around 50mph runs pretty good,

so you dont feel that its anything major. where does all of the oil go because they said they had to add a quart of oil every few hundred miles

You could have several issues,probably do..The one that I mentioned has nothing to do with oil consumption. Your rough running condition could be caused by excessive oil burning as well, with the plugs fouling. It's it's not leaking oil, it's burning it.A quart every few hundred is an indication of a worn out motor.Check the pcv valve too-that might be faulty and causing excessive oil use.