The rules of procedure herein prescribed shall govern all probate proceedings commenced after they take effect and also all further procedure in probate proceedings then pending, except to the extent that in the opinion of the court their application in a particular proceeding when they would take effect would not be feasible or would work injustice, in which event the former procedure applies. Nothing in this act [*] shall affect any limitations of time applicable to the estate of any decedent who died prior to the effective date of this act.