Just got off the phone with my local Service Center to ask about having Homelink installed prior to, or the same day, as taking delivery. The answer is "no" for those curious, you have to take delivery before you can set a service appointment. Apparently the Homelink is installed by the mobile crew at your house.
Since I had him on the phone, I asked about my delivery date. He checked and confirmed I do not yet have a VIN, and advised that "the website estimate is accurate". I had to contain my chuckle when I heard that.