Can someone please tell me how to replace the rear vents.. 1 broke and I have a spare.. and I dont see a DIY anywhere???

 

I'm looking through my info and not finding anything, but I'll keep looking.
I did go out and take a look at mine but found nothing obvious... I did notice the 2 "holes" and I suspect those are the mounting points inside the headliner/duct...

What does the replacement part look like? that may help