What should happen is, on power up you will hear the chime.
A grey screen should appear and a flashing folder would show. This would indicate no bootable drive available.
If you don't see that, then chances are the screen or logic board may have failed.
What I would do first is reset the PMU. http://support.apple.com/kb/HT1431
Try restarting it after that.
If nothing comes on the screen after that, try hooking up an external display.
Best of luck