On certain models replacing the battery could be tricky. Unless you are experienced, try talking to the agent.
If you are gonna do a do it yourself, remember if you are pushing / pulling too hard, then something is not right. (If you cant get the part removed easily, chances are there is one more nut to remove or latch to unlock).
Stone walls do not a prison make,
Nor iron bars a cage;
Minds innocent and quiet take
That for an hermitage;
If I have freedom in my love,
And in my soul am free,
Angels alone that soar above
Enjoy such liberty. - Richard Lovelace