I’ve taken on a couple faulty LCDs in the past, but have had mixed results in repairing them. I’ve had the best success when a visibly busted capacitor can be found and replaced, but this guide goes into more detail on how to diagnose and fix some other common LCD issues as well. Complete with lots of clearly labeled pictures.
http://neoxy-yx.blogspot.com/2011/12/tips-and-tricks-on-repairing-lcd.html