does the 2007 elantra have an XM unit hidden somewhere that can be replaced with a sirius unit? and would it still be possible to use the xm controls on the factory HU and XM antenna?

Not sure if you can do a 'brain' swap like you can on the GM vehicles. I called Sirius customer service and they told me to go to their web site and do a search for a 'tuner'. You will need the make and model info for the radio. I don't know how it works yet, but I plan to make the switch when the 3 months are up.

Talked to Sirius Tech this morning, and got some more info. Turns out, buying a universal tuner may not be the answer do to compatibility with xm head unit. Better to bring to installer to find where xm tuner is located, then remove or disconnect and try to replace w/ sirius tuner that fits. If you find one that connects directly into xm unit, let me know or post link.