Mont. Code Ann. § 72-3-304

Unless a petition in a formal testacy proceeding also requests confirmation of the previous informal appointment, a previously appointed personal representative, after receipt of notice of the commencement of a formal probate proceeding, shall refrain from exercising the personal representative's power to make any further distribution of the estate during the pendency of the formal proceeding. A petitioner who seeks the appointment of a different personal representative in a formal proceeding also may request an order restraining the acting personal representative from exercising any of the powers of that office and requesting the appointment of a special administrator. In the absence of a request or if the request is denied, the commencement of a formal proceeding has no effect on the powers and duties of a previously appointed personal representative other than those relating to distribution.