I have a 2007 Niissan Note. The pollen filter is accessed on the passenger side underneath, and to the right of the glovebox. It is visible, with your head in the footwell. It is grey, in my case. There is no need to dis-assemble anything.

Press down on the top of the filter, and pull out. when replacing, slide in partially, and press down the top outside corner to get it to click in. The filter should have an "UP" arrow on the outside edge.