Apparently my scan of my check engine light today says i need a new idle sensor....What is that and how much should it run me?? How important is it though??

Depends on the car......I would think.

More information please.....price, use??

The kind of car you have will determine the price (Honda a lot more $ than a Chevy, etc.)

Have you noticed any change in the idle speed when you start it up? Does it run a little rough at times, or have a loss of power?

Nope....not really.....sometimes there's a little jump when i take it out of park but that's normal i thought....I have a 2001 Ford Mustang.

About $70 and $5 for the gasket if you need a new one. I think it's on the intake manifold, on the back side. Easy to do, take it to an autoparts store and they will most likely walk you through it, a good one will even test it to see if you really need to replace it or maybe the connection is just dirty.