My son had dropped his iPod touch 4G and had tons of cracks in the screen. Remarkably, it still worked, but I couldn't stand it anymore so I ordered a replacement screen/LCD assembly.
It went well. I had reviewed a great video on replacing the screen that went into more detail than any others I had found. I watched it about 5 times before starting. Here's the link: http://www.youtube.com/watch?v=dgcmZa5dC...
The repair probably took about 2 hours but worked fine.
There are a couple of details that were not explicitly stated in the video. For example, after popping off the small metal cover of the rear-facing camera, on my iPod there was copper grounding tape that connected the metal cover to the camera back, so I had to carefully peal that off. The other thing is that removing the old glass screen was helped hugely by using a metal splurgier. The guy in the video states that the plastic tools won't work, and I agree with him. It took lots of time and care to get the splurgier under the glass. I worked from the left side near the bottom because there are no cables there. On the right side near the bottom is the cable that connects the volume and power buttons, and could easily be damaged. Finally I took tons of time to clean out all of the old adhesive from the top, bottom, and sides and replaced it with new adhesive I bought at iFixIt.