'08 Add Backup Camera w/Mirror Display and Temp/Compass

[green55]

I have a 2008 Sierra WT that I'm looking to add a backup camera that displays on the rearview mirror. I currently have the Onstar mirror with no autodimming/outside temp/compass. Just the basic mirror with Onstar. I guess the good news is I have some sort of wiring headed to the rearview since Onstar is there. 

 

I came across a mirror that has the backup cam display along with compass and outside temp: https://camera-source.com/chevy-silverado-gmc-sierra-2007-2008-backup-camera-oem-onstar-w-temp-compass.html

 

Has anyone installed a mirror like this? What am I going to need in addition to this package to get the temp/compass to work correctly? I assume I'll need the temperature sensor and some wiring? Any help would be much appreciated. I figure I may as well get the one that has the compass/temp options even if I don't hook them up immediately. That way I'll have the option to add them on later. If it is easy to add them on, then I'd just do it when I installed the camera and new rearview.