the screen had a big black thumb-sized spot right in the middle. I was going to toss it in the bin, then thought, why not see if I can make it work?
It was rather difficult to get the back off. The plastic tools provided are a bit too flexible for the task, so I ended up using a paring knife from the kitchen drawer.... The videos available to guide one through the process were very good, and made the job quite simple.
I do recommend buying a new back (as I did) in advance, as the process is rough, I suppose even more so if using a paring knife. I found it useful to have a bright light and a magnifier close to hand, as the tiny screws and the ribbon cables are quite small.
iPod nano (3rd Gen) Color Display
Phillips #00 Screwdriver
iFixit Opening Tool