Here is how to quickly replace the battery in this phone.
Sorry for some blurry pictures, I had the wrong macro setting on!
Your device lies here, waiting for the battery.
Put your fingernail in the little slot at the top, and just pull back. It doesn't require much force. There is nothing you can break really, so pull!
The rear cover removed, lying next to rest of the phone.
Pick up the battery at the end, and lift away.
If installing the battery, align the arrow with the three silver contacts, and drop it in. Put the rear cover over the back, and give it a gentle push.