I was in the same boat as you when I had my Thunderbolt. It fell from no more than 2 feet off the ground and landed at the perfect angle to just crack the screen. It was like an X on te screen, though the screen and phone still functioned fine, but it bothered the hell out of me. So I looked up replacing the digitizer and since I've opened up and built computers, I figured I would be comfortable enough to do this.
I ordered the digitizer, got it a few days later, and started working on it. Apparently while removing the digitizer (quite a bit harder to do than the videos make it look) I slightly scratched the LCD screen. but I didn't realize this until it was all put back together. I turned on the phone, and instead of the normal colors, I got some weird lines all across the screen (plus a few of them where I scratched the LCD). So I ordered a new LCD screen and had to replace that. Got it all replaced, and it looked like it was a success.... BUT there were a few area on the digitzer that didn't respond to touch, pretty much making it useless. I sent the digitizer back and got a new one. This digitizer ALSO had areas that didn't respond to touch (pretty much the bottom half of the screen).
One thing I didn't mention was that you need something sort of adhesive tape to put on the digitizer to stick onto the LCD screen on the sides, that you manually have to cut to be just the right size. It's a pain in the ass, and if you get even the tiniest dust particle in between, you'll probably need to keep removing the screen to clean it out (well you don't HAVE to, but it sure is annoying to look at).
That, along with everything I went through, felt like a huge waste of my time. I ended up just ordering a replacement through my insurance.
I hope I didn't discourage you from doing it, it was interesting to see how the they put it together and just how everything works together, just giving you my experience on the whole thing. If I had to do it again, I probably wouldn't because of how one little thing can ruin the whole thing, plus all the money I spent on the LCD and digitizers, but if you attempt it, good luck!
