[skyhammer]

You have to take out the glove box. Real easy, 6 screws ans one hex head screw that requires a pair pliers, nut driver or the proper size socket.If you buy your filters from Nissan instructions come with the filter. Jet Tech has a thread on here that shows this with pictures.
Anyway, even if you are slow 20 minutes is plenty of time, and anybody can do it.
You can bet I will be checking mine every six months, if not sooner.