N.M. Stat. § 45-3-701
Time of accrual of duties and powers.
A. The duties and powers of a personal representative commence upon his
appointment. The powers of a personal representative relate back in time to give acts
by the person appointed which are beneficial to the estate occurring prior to
appointment the same effect as those occurring thereafter.
B. Prior to appointment, a person named personal representative in a will may carry
out written instructions of the decedent relating to his body, funeral and burial
arrangements.
C. A personal representative may ratify and accept acts on behalf of the estate done
by others prior to the appointment of the personal representative where the acts would
have been proper for a personal representative.