If you are referring to the SD Card slot in the NAV unit, you cannot replace it yourself. There are MANY threads on here about how each SD Card is custom for each Clarion unit, and can only be supplied by a Nissan dealer for some ridiculous $350 price, if I recall. We usually caution anyone looking at a Leaf with a missing SD Card to either walk away from the deal, have the dealer replace it first, or get a $350 discount to replace it.
http://www.mynissanleaf.com/viewtopic.php?f=27&t=20354&p=433364&hilit=SD+card#p433364
http://www.mynissanleaf.com/viewtopic.php?f=30&t=11704&p=433065&hilit=SD+card#p433065
http://www.mynissanleaf.com/viewtopic.php?f=27&t=20317&p=432981&hilit=SD+card#p432981
http://www.mynissanleaf.com/viewtopic.php?f=36&t=20036&p=429428&hilit=SD+card#p429428