If it’s v.difficult to remove it’ll be equally difficult to press back on. A press is likely to be required, with a set of plastic dies.
Generally I can get them off with a case knife wrapped in a cloth to avoid damage to finders, I’ve had a full set all my life and I prefer to keep them in good condition.
If the case knife and determination fails I resort to a tool I bought second hand many years ago that clamps the case and presses a blade into the gap, thus allowing the caseback to be flipped off.
Might be better to entrust it to your local battery swapper or repairer?