2000 Honda Odyssey idle control system malfunction

I just had my oil changed and on the way back home noticed the engine was idling high. I took it back to Jiffy Lube and they looked under the vehicle, said I did get a "Engine Light" and diagnosed the problem as P0505, Idle Control system malfunction. I think it's odd that this happened right after the oil change. Is there a wire or disconnection problem (they said it was nothing to do with the oil change, that sometimes these things happen "after" an oil change). I've read other Q&A's and have a feel now, after disconnecting the battery to reset the computer, etc, checking wires, etc, that the Idle Air Control Valve may need to be replaced. Can I get to this valve without getting under my vehicle? What is the least expensive way to get this problem resolved. The vehicle idles and revs in Park and Neutral, and I'm afraid to drive it. Can you recommend a place to get a discounted replacement part? I have an appt. At the Honda dealership next Monday and before I go there would like to know the best thing to do, and/or if there is anything I can do in the meantime to possibly fix this problem. Thanks very much!