XM RADIO in my 2002 DTS

I cannot find any info on this anywhere in the manuals. car has nav system and the 6-disk changer in glovebox. Overhead by the garage door opener is an Alpine-brand device that displays "XM RADIO PREVIEW"...with a knob to change the genre of music from classical to country, rock, etc. Yet just above the green backlit LCD screen, this device says it is a cd-changer controller. So which is it, a satellite radio or a disc changer?

We are desperate to get tunes in this nice ride because the FM/AM reception is sooo bad. You can listen to the radio with key in ACC position, but the minute you start the Northstar up, the radio fades into static and extreme poor reception.

no where in the radio do I see a place to switch to XM. The choices are am, fm, and wx none of which work worth a damn. The factory CD Changer does however, work fine.

ANY help with this other device will be greatly appreciated!