I realize this thread is a bit stale, but I thought it couldn't hurt to confirm that the SD card can be replaced. I just bought a gently used 2012 Nissan Leaf last week and the dealer took out the SD card to protect it but ended up losing it. I made them order another one as part of the sale. I've been driving the vehicle for about 5 days without navigation, radio, bluetooth, etc. The card showed up today directly from Nissan. I unpackaged it, put it in, turned on the vehicle, and all works as it should.
The dealer told me the card cost $450.00, but the price directly on the package states $250.00. Whatever the cost, they are replaceable and can be ordered from Nissan.