As Trustee, you are allowed to hire experts to help you in your duties. You should consult with an estate planning attorney who can review the trust to determine what prerequisites must be met in order for your siblings to remove you as Trustee. In most cases, the trust will pay for the legal fees incurred by the Trustee.
The attorney can also advise you about making distributions from the trust. As you stated in your question, your mother funded the trust but your siblings are beneficiaries of the trust. As beneficiaries, unless the trust states otherwise, your siblings do have rights to information and possibly distributions.