iPod 4th generation battery replacement
15 Minuten - 1 Stunde
My old iPod was unusable because the battery was dead.
Following the instructions from ifixit it was easy. The only difficult was to separate the original battery from the iPod because the strong glue. The tools from ifixit were very useful, specially the spudger.
Just to emphasize the difficulty of knowing a priori how to correctly separate the original battery and doubt whether it would break something strong that is stuck.