The hard drive in an iPod Classic (12GB 7th Gen.) showed signs of faliure, so it needed replacement; whether it was the hard drive or the unit itself. Why should anyone lay-to-waste an otherwise perfectly functioning iPod?
I replaced the hard drive with a matching Samsung SpinPoint HS12YHA hard disk.
I am not familiar with the other iPod classic models, but getting the first tool you use (on each side) to pry open is VERY difficult at first. The space-of-separation is hair-thin, and scratching the metal casing appears inevitable. I would suggest they make much more resilient plastic ipod opening tools. I also suggest to anyone working on these to take the advice of using the putty knife to wedge this open. The main difference in my experience is that I used the metal spudger from the get-go. It was required, in my point-of-view.