After several years of non-stop use and goodness knows how many thousands of charging cycles, my NW-A3000 finally gave up the ghost. Knowing the incredible expense of sending things back to makers for things like a new battery, I was very pleased to find this replacement at a very, very reasonable price. I had resigned myself to buying a new machine, but I didn't have to.
Once it arrived, I set to work with a penknife and tweezers (not state of the art equipment but all I had) and I was very grateful to the previous reviewer for his tips. I shall add my own. Sony certainly stuck the original down tight, and it takes a bit of prying off (that's where the penknife came in; any round-ended knife from the cutlery drawer would do equally as well). Don't worry about force, the Sony is built like a tank. Take care with the connecting wires though, they are very thin and the actual connector is tiny. Once lined up though, the tiny plug clicks into the socket and the back can be replaced.
Once charged, my Sony was as good as new and the replacement battery seems capable of at least 10 hours non-stop and maybe much more, because I haven't gone longer without recharging.