The backlights in the screen are LEDs and are a part of the screen assembly and cannot be individually replaced. The complete display assembly would need to be replaced.
Here is the service manual that will help you to replace the display assembly if that is what the trouble is.
It may not be the screen, it could also be a faulty lid sensor or a backlight power fuse or a loose eDP cable connection (video cable).
To try and test the lid sensor, connect an external monitor to the laptop so that you can navigate through the settings and change the lid switch setting to do nothing. Save the changes and restart the laptop and check
It may be better to purchase the schematics for the motherboard to help determine where the problem is first. (I couldn't find a free download - also verify that I've linked the correct motherboard i.e. Compal CAZ30/CAZ40 LA-E111P as printed on motherboard itself).