MONTPELIER, Idaho (AP) Two officials say they are going to Louisiana to question an admit ted murderess about a two year old Idaho slaying of a Minnesota marine. Bear Lake County Sheriff Clif ford Skinner and prosecutor E bert Gass declined to say when they are going, however. They want to talk to Mary Cath erine Hampton of Sandy Hook, Ky, who the two men claim recently admitted a killing near Boutte, La. New Year's 1959. Hall was acquitted and Spencer is awaiting execution in Florida for still another murder. Gass and Skinner said that since Miss Hampton was known to have been in Idaho in 1959, they want to ask her about the murder of Marine Pvt. Wayne Siegel of Fort Ripley, Minn.