How do I access the antenna without ruining the headliner?
That is the only way to get to the sirus antenna,but more that likely it is not the antenna,it will be the reciever or may need to have it updated,meaning call sirus with your reciever number and let them reboot it.
FM is also out, it just buzzes. XM sent a refresh signal a couple times. I messed with the wire harness through the rearmost seat belt hole and got music for about a week. Thanks for your time.
2012 GMC Acadia Denali