XPS m1530 LCD Backlight Not Working

So I've had my XPS m1530 for almost 2 1/2 years now, and although it's a little beat up (no battery life, front panel held on by duct tape) it's at least continued to be fairly usable (as long as I keep it plugged in, that is). Until now. Maybe around a week or more ago I noticed that the left quarter of the screen looked a little dim. Not too bad, but it was a little difficult to read text on that part of it. Over the next week or so the dark part seemed to keep spreading until it covered everything but maybe the right 1/3 of the screen. Then it failed to come on at all, first a few times temporarily and now finally permanently.

In bright light I can still see extremely faint images on the screen, indicating it's just the backlight that is out. I am able to use an external monitor without any issues. Sometimes when the screen comes on again after being off, such as when the computer boots or when I switch from an external monitor, the backlight will come back on for about a second or so but then turns off again.

I'm running XP and my graphics card is an nVidia m8600, the driver is fairly up-to-date (didn't update it right before the problem or anything). Had the latest BIOS revision (A12), tried updating it anyway but of course that didn't do much. The brightness controls on my keyboard do nothing, can't see well enough to change them in the BIOS.

My warranty is expired and I really can't afford a new laptop right now so my only option is to repair it myself. After browsing around on various forums it seems like there are several possible causes for this. Some people have recommended replacing the inverter, which seems fairly easy and cheap but it lookedlike not too many people have had much success with it. Of course replacing the backlight itself is also an option, but that seems fairly complicated (I know my way around a desktop, but don't have much experience with laptop repair) and I wouldn't really like to try it unless I know that will solve the problem. I've also heard this could be a problem with either the graphics card or motherboard as well. Based on the symptoms I've described, can anyone tell me what the most likely problem is?