You need to diagnose the issue. The blue stuff at the top of the logic board looks like liquid damage, clean this with 95%+ isopropyl, and check the bottom of the board.
The only reason replacing the display will resolve your issue is if liquid was spilt over the screen (damaging the screen PCB and cable). There is no way a drop could cause the backlight cable to disconnect, it is plugged in snug to the screen PCB.
If you do not know how to diagnose and microsolder this, or don't have the tools, save yourself the time and send it somewhere. There is no point progressing further if you cannot do anything to fix this.
It will either be the LCD connector, LCD cable, backlight IC, feedback trace, backlight fuse or another issue with the backlight circuit. Check the LCD connector and cable for burnt pins. Check continuity across the backlight fuse (no power connected), it will beep if good. You will need schematic and board view file for your particular board to diagnose this, but generally look for where there is liquid damage on the board.