Posted by Fat Boy on February 21, 03 at 22:06:46:
I don't have OnStar and can't verify that this works, but I found this while looking for some info on my '97 Grand Prix GTP.
http://www.clubgp.com/forum/topic.asp?TOPIC_ID=6448847&FORUM_ID=1&CAT_ID=1&Forum_Title=ClubGP+%2D+General&Topic_Title=Connect+your+laptop+to+Onstar+GPS