2001 Porsche 911 Carrera Cabin Filter

I had the car service with an all points inspection back in June. I do not think they replaced the plugs, but changed the oil and air filter. However, they wanted me to change the cabin air filter, but I did not do it. The car does not smell or anything, but sometimes when I am on the highway, the car gets hot inside (even though I have to shut the fan off everytime I start it). I cannot find or have any idea of how to change the cabin filter myself since it can't be a big deal although I can't find it in my Nissan Murano either. Can you give me an idea of how to get to it?