Make sure to check and see if the car had an ONSTAR system! It WAS optional with the 2000 Chevy Impala...
http://consumerguideauto.howstuffworks.com/2000-chevrolet-impala.htm
I don’t know exactly how you’d go about contacting the company, but there must be a way to find out. If you’re not sure, call Onstar and ask them how one would find out. Even if they didn’t have an account activated, there might be a way to enable the Onstar gps if it’s included on the car...
http://www.onstar.com/us_english/jsp/index.jsp
No cell phone - no on star. Checked. This is exactly the kind of question I was asking for,