if it was for a 33 gtst i could tell you how to do it without removing the front bar.
I'll tell you anyways, unscrew all the bolts holding the housing inside the engine bay, take the front inner plastic guards off to gain access to the bracket inside the front bar. you can keep the guards on but you will have to flex them to get to a bolt. whichever is easier for you. the headlights are bolted to a bracket thats bolted to the chassis at the parker ends. Just unbolt the bracket. you could leave the bracket on and unbolt the two philip head screws holding the headlight to the bracket but you might snap a plastic pin that is used to line things up....i snapped on one of mine so i suggest you keep the bracket screwed to the headlight and just unbolt the bracket from the chassis.
I dont see why it would be any different for a gtr but you never know.