The OT is not superceded by the NT but it clearly doesn’t portray the Gospel in the light the NT does. Alot of understanding is needed to grasp the message of the OT, as an OT graduate I can say it’s very difficult. Can a bum understand covenant theology and the theology of original sin, herem, etc.? Maybe. Can a bum understand that Christ was God’s son who died for humankind? Definately, whether he or she agrees or not they will understand that to be the message of the NT. The Gideon’s use the NT as a primary evangelism tool for a reason. The stories of Jesus and the Apostles is well known to most Western people, despite their faith. The OT for me is the most intriguing, why? because it is so unbelievably full of mystery. Say what one will, but the NT is going to bring the road to salvation more efficiently. The OT can be learned later to explain the mysteries of faith, the origins of the Christian faith, etc., etc… And this must of course be done.