What will I need to do to petition the court to transfer guardianship of my elderly aunt?

Do I have to have an attorney to petition the court to transfer guardianship of my elderly aunt from an extended family member? I am concerned of how he has handled her financial estate and property, as well as her medical attention. Also he does not allow my aunt to have a phone to contact other family members. He appears to be deceptive when we ask questions about her estate/affairs. Also my aunt does not like him or trust him. She has repeatedly asked me to oversee her affairs. She does not want to be managed by him. She does not get along with the guardian. He often avoids communicating to her. Again he appears to be very uneasy and not trustworthy when we approach him about her welfare and estate.