i have a 2004.5 g35. i want to change the head unit but have heard i cannot because the ac and other things are wired into the stock head unit. sounds stupid but is there any truth to this?

 

There is a kit produced for that vehicle that retains all of the AC functions, as it includes a new AC controller. At one time it was true, changing it meant either doing massive custom mods or importing a dash panel from a Skyline from Japan(i've done both). Now that Metra makes the kit it's much easier. You'll also need the wiring harness, antenna adapter, and steering wheel control adapter if you'd like to retain those functions.