^^^^John is right. I could not find that picture. There is obviously a reason they placed the fireplace outside that paneled area and I would be hesitant to just "cut into it" without extensive investigation to see why the factory didn't.
Looks like you could just order the OEM fireplace and "whoop" up a little cabinetry and be in business. It still appears that the fireplace option was an "add on" outside the planned interior so shouldn't be too difficult hopefully - but, they are nice.
I see the LP detector was moved from the panel where the fireplace will go to the partition between the closet? doors and the bathroom/bedroom? door.