15 minutes - 1 hour
After nearly 10 years, my trusty iPod was no longer holding a charge, and had some other issues that seemed to be related.
As I expected from other reviews, the plastic spudgers that come with the kit were not worth using. I used a very small flat screwdriver to open a gap between the front and back case that was big enough to get the blade of a slightly larger screwdriver in, with which I was then able to separate the cases. Chewed up the plastic a little, but that's a small price to pay for an iPod that works again (doesn't show under the case I keep it in anyway). Opening the case was definitely the hardest part. Tiny Torx driver that came with the kit made it worth the few extra dollars, despite the flimsy spudgers.
Just go for it. I spent a long time being really careful trying to open the case & getting frustrated. It took a little more force than I was comfortable with, but after that everything went smoothly.