Follow the ECU guide below to get to the front lighter socket, obviously dont go as far as removing the ECU lol. Although when I fitted my nav my friend with very small hands managed to get his hand up behind the panel and pull the wires down and then get them back up when we had finished
http://www.technosquareinc.com/350ZECUremoval.htm
Havent tried to access the rear power socket but this http://forums.nicoclub.com/12v-power-outlet-removal-t516807.html says
"It's better to do with the cabin warm, so things don't start to break. But just pry on the bottom a little and it should pop loose, and the top just hooks into the back of the panel. If you have a plastic pry tool it may be easier, or a screw driver and a rag."