PowerPC :: What Part Of My Powerbook Is Damaged?

My powerbook G4 aluminum was dropped about 18 inches. The display is now hosed. Thus far I have found *nothing* wrong with the laptop except for the internal display only shows gray horizontal lines with black snow/static intermixed (still in horizontal lines).

What I'm thinking is that the display is probably actually fine and there is some little logic board in the display casing that is bad.

Here is what I've proven:

1. external monitor still works fine (means vid card is fine?)

2. swapped internal displays with another powerbook and was fully functional (means it's something in my display casing or my display itself)

3. backlight works fine (on my munged display)

4. i can see movement in the grayness when i move the mouse pointer around almost like the pointer was as wide as the screen and 90% translucent (i.e. there is a horizontal shaded bar i can move up and down with the trackpad)

I've already thought about upgrading to the 1440x960 display and being done with it. But then I started thinking it is probably a $40-50 part if I could just narrow it down.... And that would be the smart thing, rather than spending $300+