Worked! Though I'd say it's an intermediate difficulty, not a 'difficult' one.

Blow-dryer thing in the beginning worked well. Kitchen knife with a flat blade worked well too. You can use a cloth as a 'glove' to hold onto the tube of the bud that holds the foam pieces that go into the ear. Then work the blow dryer in stages. My buds never got too hot.

With one of the buds the flat ribbon cable would not come out at all. It is possible to leave it in and work the old battery from an angle.

Before you glue the buds shut, again give them a test run.