You probably will also get a letter from Sirius-XM about your trial subscription. That will include all the receiver details. I promptly disregard files this letter as I find that the sound quality of XM is so poor, that I choose HD radio/Pandora/aha/iPod over XM anytime.
I've had XM in my previous car for about 10 years and also added it to my wifes car... love it... I'm just going to move my subscription over to the TLX. I'll try out the HD/cell items to compare as well. Thanks.