if anyone still cares about this, the directions are turn by turn they are supposed to download to the car, and you will hear them as you need them. heres the thing on the onstar web site:
http://www.onstar.com/us_english/jsp/plans/tbt.jsp, watch the demo if you want, it shows it. Next time an advisor starts telling you all the directions tell her "Shut the f*ck up stupid biycha nd download the directions to my car!" that should work out just fine.
