That's a bit confusing on your last question.
Your original questions asked if an Xbox 360 guitar works with GH3, saying you do not want to purchase another guitar. I'm assuming you mean the guitar from GH2, and yes, as itotallybelieveyou stated, it does work.
Now you are asking about wireless working too and stating that you do not own a 360. So do you not own a guitar from GH2?
If you don't own a guitar, then you can get the guitar that comes with GH2 or GH3; though I don't like the one that comes with GH3.
Also, wireless works with an Xbox 360 elite. Your controllers are wireless. Not sure how it interfaces with the other Xbox models.