**update** in case anyone else goes through what I am (base model OEM head unit swap to GPS/Nav).....
After some research, I figured I'll need the following:
25975M ANTENNA ASSY-GPS (GPS Antenna and cable)
27960+A ANTENNA ASSY (Sirius/XM antenna housing)
28051 TUNER UNIT-AV (Sirius/XM tuner)
I'm thinking that's it for the GPS & Satellite radio install. I assume the GPS antenna/module will run along the passenger side with the stock antenna wire (28242M), found a pic of what could be the actual GPS wiring:
As for cost, I found the satellite tuner (28051) for $100 on eBay, lucky enough to find one WITH the wiring (used but oh well).
The GPS module/cable (25975M) is about $83 on NissanPartsZone.
I'll update as soon as the parts come in and I install.