I've got a 6th gen iPod classic that doesn't work when it isn't plugged directly into a power source. When I have it attached to a charger it works fine and it says the battery is fully charged, but as soon as I unplug it the thing dies. I'm guessing that this means that the battery is dead. Does that sounds like a reasonable assumption, and if so what's the easiest/cheapest way to replace an iPod battery?