have I damaged my motherboard or just faulty LVDS cable?

well yesterday i got a replacement palm rest i ordered from ebay for my Precision M4800 and i dropped a screw in the system i dont know for sure if it was in standby or windows decided to kick itself out of it (does that often because fml) it didnt appear to have shorted anything and the system never shut off like it normally would in the event of a short. But after that the lcd has not worked correctly ever since.

If i disable the switchable graphics i get no image at all unless i connect an external monitor. with switchable graphics enabled the screen works sort of, it wont display the bios unless i connect a VGA monitor but windows boots and works fine but running a game results in very very poor framerates and the CPU fan screams after a few seconds. and device manager no longer reports the corrects LCD panel in the system just says generic 1024x768.

DELL's diagnostic reports this error "UNABLE TO ACCESS LCD EDID EEPROM" and alot of people are saying just replace the LVDS cable which is 16 dollars no big deal but the fact i dropped the screw in the system makes me question the motherboard which is 90 dollars.

I dont think it's the nvidia card because i completely removed it and still had issues and the diagnostic still reported the error.

Everything works flawlessly with an external monitor absolutely no issues whatsoever, windows reports the correct monitor and everything. even the HDMI works and i ran a game for a while ran full speed without issue. with and without switchable graphics enabled so im not sure if its a damaged motherboard or just a faulty cable which would be strange because i never even touched the cable once while installing the palm rest but its old so not outside the realm of possibility.

any ideas?