You will need to remove the door panel first, then take off the door handle while it is off of the car.
Try this:
Video #2 Audio Install in a 2009 370Z on Vimeo
It's about 2 minutes into the video. Courtesy of SlikNik
You can get the plastic interior remover tools even from walmart, if they have car audio install tools. I got my set from harbor freight for a few bucks and it has 6 pieces.
hope this helps