6.4 gpcm location/glow plug removal

Hi guys, I just got a P0672 code and will be replacing the #glow plug... so first off, does anyone have any tips on the easiest way of accessing it. I took a quick peek tonight and it doesn't seem to bad if I remove the antifreeze tank.

Secondly, I have been reading about this code and some people say there can be a problem with the control module. I was wondering where this was located and if this could be the issue? For the last few months I have noticed when I turned the key and let the plugs warm up there was a loud buzzing type noise (not the normal hum of the glow plugs warming up)

Thanks!