I installed the second floor and fireplace assembly today. I deviated from the instructions and installed the fireplace assembly into the second floor opening before installing it on the dollhouse. I decided to do it that way because I wanted to be able to finish the fireplace more easily. Once it's in place, it's much more difficult to do so.
I am just using a simple, white painted finish for the fireplace and the same stone printed paper, I used for the foundation, on the hearth walls.
Once the fireplace was installed, I installed two more walls.