1. PLEASE DON'T THROW AWAY A WORKING MAC!
2. Have you tried connecting the 2 grey wires? Strip both ends of them and twist them together. Then, secure it with some electrical tape. REMEMBER TO DO THIS WHEN THE COMPUTER IS OFF. Does anything work?
3. If it doesn't, is your inverter working? Can you try swapping the inverter for your screen?
4. This is extreme, but you can go buy a whole new display assembly and swap it out. It would be a waste to just throw away something that is still half working.
5. Turn it into a desktop computer. Get a display, and hook up your PowerBook to the display using the video adapter (can still be found on Apple's website store). And you have a nice desktop computer until you can fix it.
Hope this helps!