Jesus' statement, "because I am going to the Father" should likely be seen in relation to his role as "the sent one" (cf. 3:17; 4:34; 5:23; 8:29). That is, the one who was sent is now portrayed in 14:28 stating that he is going back to the one who sent him. Therefore, Jesus' words likely signify that his mission will soon end. If Jesus' mission will soon end, then his disciples would have good reason to rejoice. Finally, it is likely that when Jesus speaks of the Father's greatness, his words should be seen in light of John 10:28-29. Jesus' words would then point to the reality that the disciples need not fear (14:27) because the Father is fully able to protect them (cf. 17:15).
I suppose one of the things that can be learned from this is that there is a serious difference between exegesis and eisegesis.