This was super easy to install in my 2013 Acadia.
1. Remove the little carrot area cover in the back
2. Remove the 3 bilts from the plastic piece closest to the back seat, and take out the plastic piece
3. Remove the plastic piece covering the latch in the very back (it just pulls off)
4. Remove the two D-ring covers on the passengers side and remove the bolts.
5. Bend the back panel out and you have plenty of room.
6. Remove the 3 torx screws holding the unit in, replace, and repeat steps 1-5 in reverse. Took less than 30 minutes and the rear HVAC works again.
