LED backlight conversion kits are a thing that eBay is full of these days, so, sure, it's probably doable. (Those monitors are a bear to take apart, though, just like anything else Apple since 2001.) Of course, reading up on them a significant problem with these conversions is the spectrum from LED lights differs significantly from the original CCFLs, so in all likelihood the monitor's color calibration is going to be irrevocably blown. Probably not a big deal for casual use, but still something to think about if you're considering buying the monitor for any sort of "production" use. If you just want it because you want a matching monitor for a G5 that's a "collector's item" then, sure, not a big deal.