I just received my n2 off ebay and i want to test it. what wire do i hook up to the battery to see if the screen will come out and retract? do i have to hook it up to the brain?

Not sure about the N2 since I have a D3 but to test out most radios you will need to connect both the yellow(constant 12V) and red (acc 12V) wire to the battery and the ground to the the negative terminal/ground.

thats what i thought just like aregular radio but it seems that the red on this is labeled ill and the yellow is battery.

No, dude. You might be colorblind or something. That wire that says ILL on it is your illumination wire, and it is orange. Connect the wire that's marked "+Battery" and the wire marked "Acc" to the positive terminal, and the black "Ground" wire to the negative terminal.