I prefer to use grain of wheat bulbs and the best source I have found is Model Power's Peel & Stick Lights. They offer two sizes, the 510/511 for N & HO and the 520/521 for O & G. To me, the smaller lights look about the right size for a bare incandescent light bulb once in the building. On the hardware store I used two of the peel and stick lights and adhered one each on the lower level in front of the ceiling fan that is printed on the back wall. I took the bulb out of the peel and stick base, drilled a hole just large enough to pass the wires through just under the fake light shade over the Harrisons sign and super glued the bulb is place. I also drilled a small hole under the front awning and placed a bulb there. A fifth bulb was placed in the upstairs. I kept the background and the paper blocks in the upstairs because I felt the black paper allowed the upstairs rooms to just have a faint light such as a bedroom might have. The end result gave a very nice effect.
If you are planning to detail the interior, I would remove the printed background but if not , I find the printed background to be quite believable.
Good luck and happy railroading,
Don