help installing new headunit with navigation

[duck]

hello....
I didn't have a problem installing my eclipse AVN headunit into my last car (subaru impreza) but i'm a little hesitant with the yaris.
I've looked over plenty of technical specs, bought everything I could possibly need, but I just wanted to check a few things...

Is the ECU/ECM under the hood? Will I be able to get to the Vehicle Speed Sensor (I believe it's violet/white) easily without removing anything? I need to tap it for the navigation. If it is under the hood, where are the holes in the firewall for me to run the wire into the interior?

I believe I have everything I need to remove the headunit.

what's the best wire to tap to simulate grounding to bypass the safety feature so i can watch dvds while driving (no i really don't plan on doing this, but i don't like restrictions). I was planning on just tapping into a ground on the wiring harness itself.

Lastly, I will need to run the GPS antenna to the top of the trunk. What is my best path? I'm planning on running from the headunit across to the door sill and underneath the carpet probably on the driver side.

thanks for any help you can provide