A guardian's authority and responsibility terminates upon the death, resignation or removal of the guardian or upon the minor's death, adoption, marriage or attainment of majority, but termination does not affect his liability for prior acts, nor his obligation to account for funds and assets of his ward. Resignation of a guardian does not terminate the guardianship until it has been approved by the court. A testamentary appointment under an informally probated will terminates if the will is later denied probate in a formal proceeding. [1979, c. 540, §1 (NEW).]