What is forseen (if at all possible) in the process of modifying or amending an irrevocable trust held at Bank of America in Florida?

The revocable trust was created July of 1999, but my grandfather died in 2004. From what I''ve read, that means that the irrevocable trust was created at his death. I am only trying to amend (or delete) the age limit restriction of (24) which pertains to the payment of my college education. My father and I are the only beneficiaries and BOA is the sole trustee. How should I proceed if the amending process is possible by Florida state law?