How do I remove one trustee and add one or two others?

Trusts are not filed with the courts. ?As creator of the Trust your mother has to change who is trustee, you can not do it. ?Look into getting a power of attorney from her.

In California, the trust must be revocable in order to be amended, and then normally only by the person that established the trust, which would be your mother. The fact that she received assistance from you in adopting it does not alter the fact that it was a trust she created for her property; i.e., its HER trust. Sometimes a power of attorney may grant an agent or attorney-in-fact limited authority to amend a trust in which the principal is a Settlor or Grantor, but I would need to research whether that power would go so far as to altering the successor trustees. At her advanced age there may exist questions of her capacity to effectively execute trust amendments or new powers of attorney. You can make court filings at airports?

Revocable trusts can be amended. Unless you have a power of attorney allowing you to amend the trust your mother must execute the amendment.

Unless the document itself gives you the power to remove and appoint trustees, you cannot do so. Your mother, as the Trustmaker can do so, if she has the mental capacity to do so. Otherwise, the only alternative would be to go to court.