Donald J. Keller Formerly of 1618 N. Hall Ave., Appleton. Age 58, died after a courageous battle with cancer on Thursday, August 17, 1989.  He was born January 24, 1931, in Brillion; and married Mary Steffens on November 12, 1955, in Appleton.  He served with the United States Army for 20 years with tours in Germany, Korea, and Vietnam.  He was employed at the Appleton Post Office for 18 years; retiring July 1, 1987.  He was an active member of St. Thomas More Catholic Church.  Don was a member of the Tombstone-Pickerl Snowmobile Club, and the Rolling Stone Lake Protection and Rehabilitation District.  He was a member of the Harvey Pierre VFW Post No. 2778, and the Disabled American Veterans.  Survivors in¬clude: his wife, Mary T. Keller; a daughter and son-in-law: Catherine and Larry Scheider, Neenah; two sons and daughters-in-law: Kevin and Barb Keller, Little Chute; Keith and Lynn Keller, Appleton; three brothers and two sisters-in-law: Wilford, Antigo; Edward and Mary Ann, Green Bay; Elmer and Dorla, Rhinelander; three sisters and two brothers-in-law: Lyn Doris and Al Lodes, Chilton; Georgianna and Edwin Petermann, Brillion; Marcella Diener, Hilbert; four grandchildren: Michael and Nicole Scheider, Jill and Andrew Keller.  He was preceded in death by his parents: Nicolas (Ed) and Catherine Keller; a son, Karl David Keller; three brothers: Joseph, John, and Karl Keller; two brothers-in-law: Eugene Schaefer and John Diener.  The complete funeral service will be held on Saturday, August 19, 1989, at 11 a.m. at St. Thomas More Catholic Church, 1825 N. McDonald St., with Father Gerald R. Falk officiating.  Interment will be in Highland Memorial Park.  Friends may call at the Wichmann Funeral Home, 537 N. Superior St., on Friday from 4 until 8 p.m., and on Saturday from 8 a.m. until the cortege leaves for the church.  A prayer and scripture service will be held at 7:30 p.m. Friday.  A memorial fund is being established.