Ok, so REALLY enjoying this build. So, I put alot of detail into the interior but of course when I test fit the fuselage, all that disappeared. Then I got it in my head that maybe I should light it. I spent a couple of days figuring out how and googling, etc. I have NEVER worked with any kind of electronics before today. It was actually easier than it was made to seem.
Step #1: goto Radio Shack. Find the nerd and ask him how to set up a simple LED.
Step #2: buy the Breakaway Breadboard, LEDs of whatever color, and Battery Pack that he/she gives you. If they are nice they will set it up for you in the store.
Here's what i came up with in the end after a couple hours planning and drilling.
this is the breadboard with the LEDs in series. all you have to do is plug them in the same way (one pole is longer than the other). Plug the battery pack in to match red-red, black-black (pos/neg). I drilled holes in the "ceiling" on the interior with a Dremel and a bigger-ish drill bit. The holes were made to fit the LEDs perfectly.
Here's the basic effect. I put the battery pack underneath the roof. It fit nicely (lucky) and it looks like a piece of internal equipment to the helicopter.
I put the battery pack in such a place where I can take the battery out easily and within reach of fingers.