What is the code for the 2007 NAV disc for the system in the XLR? The gmnavdisc.com website gave a code for 2008 (28561392) but only said SALE on the discounted disc (15923893). Is 15923893 for 2007? My goal is to buy a newer verison for my mum in her 2004 DTS, which uses the same system as the XLR. With that being said, if someone got thier upgrade for 2008 and sell me thier old, nearly worthless 2007 verison, that would be great! PM me please!