If you get weird colours or it's black but fully lit up, then its the TCON board (the LCD controller). These are easy to replace as they're usually on their own

If you get weird colours or it's black but fully lit up, then its the TCON board (the LCD controller). These are easy to replace as they're usually on their own board and you can just swap it out for a new one. If you get the full image but its dark (you can hold a flashlight to the panel to see), then it's the LED strips. You simply take off the panel and replace the strips that are broken (though you should probably just replace them all). Fairly easy to do. Rarely it could be the PSU that drives the LEDs, but that would usually mean the entire screen is dark. TVs are actually quite nice to work on. They usually have big circuit boards which are nicely labeled and enough space that you could easily replace a capacitor or two with a soldering iron. :)