ok i just bought the ROEM-GM21A from pac on ebay to install my pioneer head unit into my escalade with bose. i could care less if the onstar works because i dont use it and dont even have membership, my question is, is there an adapter for the plug thats in the dash for the factory cd changer to plug into the auxillary jack in the back of my pioneer unit?

Nope. When you replace the factory radio, the cd changer becomes unusable. Your best bet would be to find something else to go there, like a pocket or single din dvd player or something.