It's not terribly difficult to do, it's just very time consuming because you have to completely disassemble the LCD panel to get at the CCFL tube(s) without damaging the panel. It usually takes me a few hours to rebuild a LCD screen with LED backlights.
Get some neutral white LED tape like this:
https://www.ebay.com/itm/332745344064
You'll need to determine how much space you have where the CCFL was. Laptop screens are usually pretty thin, so the smaller 5mm tape may not be thin enough, requiring you to either find or make a PCB with SMD LEDs that's thin enough to fit. I find that 5MM tape works in most cases. The larger 8mm tape usually works in older square desktop LCD monitors, just make sure you don't use the waterproof variety. If in doubt, take the panel apart first to get measurements.
You also need to make sure you get the more densely packed LED tape with 600 LEDs/m vs the 300 to give both a more uniform brightness and prevent bright spots on the screen. Another good idea is to find the tape with the largest LEDs installed, like 5050, which are 5mm square. Tape that has pencil thin LEDs doesn't look as good, but you may not have a choice due to size constraints. 5mm tape usually has 2835 LEDs, which work well enough.
In any case, the rolls of LED tape are cheap enough, you can get multiples to experiment with.
And a high voltage buck converter like this:
https://www.ebay.com/itm/263372679565
A high voltage buck converter is important because power sources in LCD panels tend to be 25-50v and normal buck converters can't cope with it and will burn.
From then, it's just trial and error. You'll need to find a sufficient power source inside the screen/laptop to cascade the buck converter off of and then set its output to 12v before you attach the LED tape.