You can zap the PRAM, but do the basics first. Check the connections, unplug and replug all connections (video and power). Make sure that the brightness isn't turned all the way down too. I know that sounds dumb, but that was the issue for a friend who thought her iBook was broken.
It sounds like you are just not getting video signal. If you want to zap the PRAM, you do it by holding down CMD-OPT-P-R immediately folloing reboot and hold down until you hear the start chime. Hold until you hear the chime 3 times.
I don't know if that will help.
Good luck.