Guenther is a graduate of the University of Illinois, having earned a Bachelor of Science in physical education in 1967 and an M.S. in administration in 1968. Guenther also played football at Illinois, lettering in 1965 and 1966 as an offensive lineman as well as being named second-team All-Big Ten and the team MVP in 1966. While at Illinois, Guenther was a member of the Kappa Sigma Fraternity.