Hi Pierre,
The silicon will help in the short term.
They pop out very easily with a small screwdriver, coat the new ones with clear nail varnish and rinse your handsets after every dive in fresh water moving the switches up and down to get the water behind them.
When you remove them you can check the polarity orientation by that old saying opposites attract.
And as a warning to most people don't rinse them in dive shop/clubs rinse tanks as they are invariably full of saltwater. A monthly strip and check often helps, now spit that egg back out at your Granny guys!
Cheers,
Dave Cooper.