What are my rights as beneficiary of a trust when the trustee refuses to carry out any of the duties or distribute assets?

My sister and husband are co-trustees for my mother's estate trust. They have not provided any updates or accounting since 2013 when my mother passed. I have asked for an accounting and was told they do not have time to do it. I do not know how much is in the small estate and did not push hard because it is probably less than 30K. However, they are just ignoring their duty and I think may have kept everything for themselves. How do I solve the problem without incurring a lot of legal fees? Can I take them to small claims court?