Thanks everyone for the comments. This turned out to fairly easy, and one of my few endeavors that came out better than expected. The most time consuming part was moving the light switch. Nothing magic there, just cut a new hole in the wall board, attach the junction box, and string the wires to it.
Jerrman. I should have been clearer in my post. The flat is made of two identical photos, one on top of the other. The lower layer is mounted on 3/16" gatorboard. The upper layer is mounted on chipboard, but I cut out the window and door openings. This gives a subtle 3D relief to the structure.
You can probably tell that I used Photoshop to modify the side panel before going to a professional shop to have it printed. I added more doors along the dock, I got rid of the fire alarms and fire escape, and I took out the sign and center two vertical sections.
Now that I know this works, I may try to make some background buildings the same way. The advantage of this in addition to its ease, is that your background buildings will have the same "feel" as your foreground ones.