i'm scheduled to change my oem head unit on thursday the 21st. concerns mentioned by various sources:<br> <br> 1. some fault codes activated, seen during scheduled maintenance<br> 2. fiber optics issues if cd changer oem (not in my case)<br> 3. tele-aid. this is the one that concerns me. the dealer showed me SOS in action. it seemed to work through the oem head unit when we called...muting the radio volume then feeding the tele-aid rep's voice through to the speakers. will the functionality totally disappear if i change the head unit? in other words, will the SOS still 'auto-call' for me if i (god forbid) get into a serious accident, or does it need the factory stereo to do this? although i doubt i'll be needing to manually use the SOS button, i think the emergency auto-call when air bags deploy or a rollover happens could be invaluable. thanks for any help on this!!!