I tell you, if I were running either of these companies installing this fireplace, I would be embarrassed at how terrible I was doing. This is not a hard thing, but yet...
It seems every day must be filled with some drama. This morning was to be told by the guys installing the gas, electrical (GC) that they were still waiting on the permit to be issued (! should that not already have been applied for???!) and that the inspector can't come out until it is. And that the mantel cannot be more than 10" from the fireplace ("You mean the top part of the mantel that sticks out 8 inches?" "No, the entire thing, including that which is flush against the wall."). Shouldn't someone have looked at the measurements before, oh, everything was already purchased?!?!?!? Apparently not. Unless it was me. Also, why are you guys not talking to each other and instead funneling everything through me?
I was exasperated. Karen had enough and decided it was time to bring the hammer down and had a little discussion with them and told them they need to start communicating with each other. Go Karen! 
This damned thing had better look amazing!