Thanks for the reply! After I posted I searched thru some other threads on the forum regarding the Nav system and I found mention of a web site that I went to called
www.gmnavdisc.com. You put in your car's VIN number, verify your ownership, and you can order updates for your nav system. I ordered one for my car. Price of the disc was $199. I then called them to verify that I had ordered an upgrade and not a replacement. The only way to do it (they said) was to check the part number on my present disc and compare it to the part number on the ordered disc. If they were different, it was an upgrade. I did this and the part number of the one I ordered, matches the part number you just gave me. Also, my present version is 3.0 while yours is 5.0 so I am very optimistic that I have the upgrade. My present disc shows that the info on the maps is from 2002-2003!