It depends on the fob itself. You will be sent instructions if you can program your Nissan key fob at home, which should be fairly simple to follow (if not, you can find them online with a little searching.) I'd say that it's a task worth mastering to save the cost of programming - this can cost anywhere between $50 to $200, depending on the complexity of your key fob and whether or not it has quick-start functionality. Some key fobs cannot be programmed at home, but if possible, it's a good idea to try. You can always take it to a dealership if it doesn't work out.