Hey i had a avic-n2 but someone broke in my 350z and stole it, so i will be getting my avic n3 i ordered tomorow so i need to know do i need to change the brain to the new n3 brain or just keep the old n2 brain?

to bypass the n3 you flip the switch on under the void sticker and round the brake wire right?

The N3 brain has improved XM and ipod display so I would switch it out. And you are correct on the bypass

Is the switch on the brain or the display?

the display.