Take a 1/2 drill and a sawz-all, then... :headslap: Only Kidding!
The antenna gets mounted on the roof just forward of the rear hatch, and the antenna wire is run to the satellite radio box. Check with the instructions that came with the unit, but I would think the antenna would be mounted on the roof with double-back tape. The wire would be run through the hatch opening, so it is best to mount the antenna as close to the hatch opening as possible without interfering with the hatch opening and closing.
Stop by a local Nissan dealer and see where/how they mounted the antenna.
There are other forums members who have done just what you are planning on doing. Wait for them to weigh in, I am sure they will offer some very valuable advice.
Good luck with your new MO.
I found a thread right here with pictures and step by step. It looks a little intensive for a supposed factory pre wire. I will get at it and see what I can do today. (sawzall, scared me to death)
-njjoe