I just returned from my "Head Unit" replacement. My XM ID did NOT change. It's my understanding that the XM ID is located in the amp unit, not the head unit as it is in the other Hyundai models. An unexpected item that I observed was that my navigation software is now the latest, "April 2010". I'm thinking that this must have been loaded in the new head unit when it came into the dealership. A bonus to be sure since otherwise I would have had to pay for an upgrade.