A few weeks ago I inquired through my local Nissan garage about getting the official Sat Nav installed.
They quotted me somewhere around £2000 pounds all in.
For the parts alone it was about £950 from memory, then there is the cost of fitting, the DVD software, and a couple of other bits that they mentioned.
The dealer was very helpful but recomend that I just go for a TOM TOM unit, saying the Birdview wasn't that great and I would need an extra speaker for the sound (apparently you cant have it going through the stereo if you fit it after the factory, dont know if that's true).
Im sure the price will vary depending on dealership, but I seriously don't think it is worth getting the factory one, esspecially now there are so many good aftermarket ones out there. IMO.