Frank Hardy lived among the Navajo for a number of years at La Vida Mission, which is located 50 miles below Farmington at Tsaya, New Mexico. He both studied and taught Navajo at the University of New Mexico as a graduate student. His 1979 dissertation title is, "Navajo Aspecual Verb Stem Variation." He now lives off the reservation in Westminster, Maryland.
Tony Goldtooth has taught Navajo language at the Shiprock campus of Diné College for approximately 30 years. If you Google Tony's name you'll find it in used connection with writers, researchers, and news media. Taking one specific example, his name appears in a New York Times article from 2006.