G751JY Dead LCD display/motherboard/cable? Shorted MB, Diagnostics

Hi guys, my G751JY internal LCD died, after a re-paste attempt. During reassembly, I made a mistake and plugged in the battery before I plugged the eDP cable. When I was trying to connect the eDP cable, I saw a spark between the MB connector and eDP cable. As a result, the LCD display died.

G751JY, i7-4860HQ, GTX980M, 16GB RAM, 1TB SSD

What do I know so far:

• bootup with external HDMI monitor is OK (onscreen artifacts during boot logo)

• during W10 bootup there are horizontal artifact dots and stripes next to Windows logo

• sometimes Windows 10 boots up in iGPU mode, the GTX 980 does have a yellow exclamation mark in Device Manager, showing Error Code 43 and the internal LCD backlight is off

• if I disable 980GTX in Device Manager and enable it back again, the card starts working normally on external display. I can play games, nothing seems broken, except the internal display

• In the very moment I re-enable the GTX 980 in DM, the internal LCD backlight turns on, and three wide green vertical stripes start to appear. They are barely visible first, but keep on getting brighter, until they are fully visible

• FurMark stable, CPU stress test stable, no throttling

• GPU temp 71°C full load, CPU temp 79°C full load

I assume I killed either the motherboard or the display or the eDP cable. I am seeking for advice on how to diagnose the problem, so I am 100% sure what part should I purchase to bring the screen back to life. I appreciate your ideas and input. Thank you for your help.