Hi Sondra,
A cracked soundboard may not be the end of the world. However, a warped one might just be. If the crack is causing a vibration or an odd sound, that is a problem.
Replacing a sound board on a piano that age may not be possible. You might find someone willing to do it, but it might cost you more than what the piano is worth. It is a major undertaking.
It might be worth getting someone in to look at it and advise.
Rob