I have the same issue, i have had a little look on youtube and you can remove/ replace the padding easily as it just clips on and off.
When you do this it uncovers the screws. I would suggest that the battery replacement is fairly straightforward from there however you are gona want a reliable battery from a reputable source as a battery exploding in you headset would not be fun!
I havnt done it as ive no idea how to source the battery .