I'm looking to do the same thing. I'm getting ready to order the battery box (I have lots of rechargeable AA batteries), a few 20" extension wires, and some of the lights. According to lego.com, you can run "several hundred" lights off one battery box. The lights fit inside a 1x1 trans colored cylinder brick if you want to colorize the light. What I'm wondering is how bright a single light will be inside the building. Guess we'll find out.