Ender 3 display stopped working, how to test if need to replace
This is hard to answer, it depends on your skills if you can can repair it or not. As you haven't changed the firmware, it is unlikely that this is a software issue. If the display doesn't light up, the power to the module may be broken.
If you have an Arduino Uno or similar you can try to upload a sketch and connect the display to see if it works, there are plenty of sites explaining how you should do that (software sketch and hardware connections) based on the pins exposed on the EXP port. Note that you can forget the EXP port that controls the SD card.
Personally, I would just buy a new controller, they are cheap (found on those typical Chinese vendor or auction sites).
What you can do is check whether the printer board still works, if you connect a USB cable directly to the board and connect it to a PC, you could see if the printer responds using a printer application such as Pronterface (part of the PrintRun suite).