How do you replace the cabin filter on a 2004 Nissan Frontier?

Remove the glove box door (six screws). Remove the metal spring clip that hold the two filters into the air duck directly behind the glove box. There are two filters, one above the other. Pull the lower filter out first by pulling it directly toward you. The top filter will slide downward to the bottom of the slot. Pull it out also. Replace with two new filters, but putting one into the slot and pushing it upward to the top of the slot. Then while holding the top filter in place, push the lower filter into position. The lower filter holds the top filter up in place. Replace the metal spring clip on the lower filter.