Help removing rear panel and/or door pillars

[Shoulders]

I have an 05 Sierra regular cab, and thanks to all the great information on this site I have been able to replace the factory head unit and not make it look like a Frankenstein transformation.

 

My problem is that I have also installed a CB and I need to run the antenna lead into the cab. I suspect I can bring it in through the vents on the back of the cab, but I can't see how the rear panel comes off or if the door jam pillars have to come off first.

 

I would like to keep this truck intact, so I would rather ask and be thought an idiot than to go ahead and do something stupid and prove it.

 

Any help is greatly appreciated.