Both answers from Slava and Isreal are correct.

I would say that:

opportunity means that something is possible

probability is a mathematical way to express the degree of possibility

I will never have the chance/opportunity to fly to the moon.

It will never be possible for me to fly to the moon

The probability of me flying to the moon is zero.

An opportunity is a given chance 

A probability is a possibility

P.S. I am probably saying the same old thing haha