Sorry I didn't get to post earlier; I've been out of town for the holiday.

Murphy's Law interceded in the installation. While the SIRIUS/Nav integration "fit kit" indeed has a part number, the dealer called to say that, "Oops...he was wrong." The part can be ordered but is apparently physically unavailable now "until May." He received the receiver unit, and he said he'll contact me when the fit kit part arrives.

::sighs loudly::