Take a look at this thread,
http://www.norgetech.com/navsup.htm it will help you identify where to get to wires. The info is for a oem nav, but there are many similarities to an eclipse as they are both made by fujitsu ten.
As for where I grounded the wire. When you check the pics in the link, on the photo where it is the center console with everything removed. I found a nice bare metal area with a bolt on the far bottom passenger side of the console area. With everything removed, you will see what I'm talking about. I then looped the wire up to the center console arm rest area and mounted the swith inside the arm rest storage area. The swith is a simple interupter, when on, the nav thinks your in park because the ground loop is closed. Flip the switch and the loop is open and it will not play dvd or allow you to input address's or destinations while driving.
Now to be responsible, I only did this mod so that a passenger can input address's while driving. NOT for watchin dvd's while driving