What about you keep the factory radio with all the factory features working
and you add a bluetooth interface with USB and iPod controls also bluetooth for music and the phone
caller ID will be display on the factory Chevrolet Trailblazer factory radio
http://www.oemautosound.com/pc-781-139-oem-usb-interface-for-ipod-iphone-android-smartphones-gm-03-13-vehicles.aspx