How do I fix the lighting thing on my iPod?

Heather, number one thing to do is to disassemble your iPod and clean it. Otherwise you are running the risk of corrosion failure. Clean every part with 90+% of isopropyl alcohol and a soft brush. Once you got that done, replace the battery. Any iDevice (and others) should have their batteries exchanged for a new one to prevent failure or worse due to the exposure. Once you have that accomplished, reevaluate. It is possible that this is caused by the backlight IC or the backlight coil, but it is also simply possible that it is the actual backlight in your display. That is the easier one to change, get a new display first. Consider the backlight circuit in simple ways, the LCD is the bulb, the IC is the light switch and the coil is the power source. Take a look at the teardown to see if you might want to tackle it. If not, you might try a service to do that job for you. Hope this helps, good luck.