Lap display problem -- need help with diagnosis, please.

I need assistance determining which part needs to be replaced on my Sony Vaio VPCEE23FX laptop.

Facts:
The monitor was "blanking" intermittently. When I would move it a little it would come back on. The problem progressed. Now, the monitor rarely comes on.
The video output to a different monitor works fine.
It DOES have the backlight inverter. I've shown a flashlight on it in dark room to test if I can see an unlit "ghost" image. I didn't see one.
I have checked to see if the video cable was plugged in "all the way" on both the monitor and the motherboard. It was.
The laptop has "dedicated" video and there were some overheating problems, but they are fixed now.
It was dropped twice. The video problems didn't immediately appear after either drop.
Windows 7, AMD Athon II dual core 320 @2.1 GHtz. 4 GB DDR3 8600 RAM (1066 MHtz). ATI Mobility Radeon HD 4250.

I figure it's either the cable (due to intermittent and progressively worse blanking) or the monitor itself. I believe I am able to replace either of those two parts. However, sellers will not allow me to return the part once I've installed it. Both parts are pricey and I don't want to buy a part I don't need.

Does anyone know some way to diagnose either the monitor or the video cable?

If it was the FL inverter or the backlight tube itself you would have seen the dim 'ghost' images.
You checked the cable connections on the monitor, motherboard .. and FL inverter board too?

That only way I know of testing which part is the culprit is to test with a known good cable and known good LCD screen.
I suppose you could test the data / power cable for continuity but I'm not exactly sure how you'd go about doing that.

Rolli -- It used to flick on and off when we moved the monitor on the hinge a bit, which seemed to me like the cable. But now it just sometimes comes on and sometimes doesn't, and moving the hinges does nothing.

Hi

I own a Laptop repair company and take my word its RARELY the cable...to me it sounds like the screen.... take it to a laptop repair shop and pay them to test it....usually shops charge around 1/2 hour labour to do this..

All the best Brett

Ugh.... Now the laptop won't even boot. RAM tested, it's OK. Maybe HD is dead. I can't get into bios, but I thought I could if the HD was dead. I thought all I need for bios is RAM, CPU and video.

I will test the LCD if I can get it to boot.