What forms must I file to take my sister to court after mom dies intestate?

Sister is closing accounts claiming she is successor holding all valuable property. She sold the car without my consent. Mom was also in the process of taking her of title. She had to be on title due to section 8 requirements but, had moved out. How do I file? I need to take her to court. She is lying and forging documents. Plus mom lived 2 hours away so it's not easy to drive up to just talk to the court. I want to be prepared when I arrive. I have 2 kids so minimizing travel would be ideal.