Cool... I asked about dash lights as a lot of times people get the Head Unit earth and illumination wires confused and blow the dash light fuse.
I am not 100% on where Nissan fitters grab the power for the Sat Nav as my issues were all done under warranty but as it is ACC power then a bit of sleuthing should sort it out. I would be very suprised if they didn't use the head unit power.
Seeing as how the Head unit is working tho it means the fuse must be OK so maybe that "third" plug is the problem
As I mentioned prev to Yendor the Head Unit should be a straight swap (mine was but mine is an 07 ST) but sometimes there are issues getting the logic from the steering wheel controls set up