Val, is it definitely the gear selector release *button*
itself that is
hard to push, or is the actual problem that the gear selector lever is
hard to shift out of park once the release button is pressed? If it's
the latter, it may be that you parked on an incline without setting the
parking brake, which can make it hard to shift out of park. It doesn't
take much of an incline, either.
When you park the car, try putting on the parking brake *before*
shift into park, and see if that helps.