What is the main conflict in Lamb: The Gospel According to Biff by Christopher Moore?

Heaven assigns the task to raise Biff, a childhood friend of Jesus Christ, from the dead to an angel named Raziel. Under Raziel's supervision, Biff must write his gospel to explain what Jesus, whose Hebrew name is Joshua, did before he started preaching. Biff's Hebrew name is Levi. Both the angel and Biff find the modern world confusing and frightening, but they both like pizza that they order from room service in their hotel. They share a single room and seldom leave. The man who delivers the pizza is ironically named Jesus.