We really should create a sticky that has all the general questions answered....
What do you gain by bypassing the yellow and light/green wire?
This bypasses the system check for the parking brake. The system requires you to engage the parking brake to watch movies. By bypassing this check, you can watch movies without the parking brake being on and while moving.
Can you watch movies and access navigation by doing the bypass?
You can watch movies and access navigation anyway. The bypass allows you to do that WHILE moving.
Also, what is the best way to hook up an MP3 player?
iPod with the iPod cable. Or, you can use the aux input cables on the front of the D3
Can you use the AV jack in front or is it better to hook up an rca cable to the back?
As stated before, use the aux jack in front for easy hook up. For a cleaner look, you could use the a/v harness in the back.