Aux option on 2003 Stereo

I have a 2003 Z-71 Tahoe and would like to use the AUX option on my stereo. I have the Bose sound system w/onstar. There has got to be a way to connect to tha input. I have seen some equipment made by PAC but I do not know if I need the 10 or 12 pin option. Has anyone tried doing this?

how about this?

http://www.installer.com/aux/index.html

Thanks. I guess I just need to call to figure out which one I need.