My ipod G4 screen was cracked and falling out; the headphones only worked from one ear bud; home button did not work; and the battery died in 5 minutes.
Slow and steady allowed everything to come apart and reassemble as the guides described.
My case was also twisted which made the new screen crack after two weeks around the power button. Also, what appears to be unrelated - the power plug became loose and will no longer accepts a charge. I cannot say if that was directly from opening the case or by some gremlin. The replacement home button never did function, even though I could push the interior plunger with my finger nail. And the headphones still only work with one ear.