In regards to the Gospel of Judas, I like how Scot McKnight counsels people to approach it:
Jesus Creed » The Gospel of Judas 1: "Now, I’d like to make a suggestion: apologetically speaking, we can only do two things — compare these texts to the canonical Gospels and say “they are really different” (no one denies this). And in saying that some will be done because “really different” means “really wrong.” If you’re honest, this proves nothing: we might be dead wrong in believing those canonical Gospels as the ones that tell the truth. So, second, what do we do? I suggest this: the only substantial argument against the alternative Gospels is a confidence that God’s Spirit directed the Church (inspired the texts and preserved the texts and led the Church to recognize the texts) to the canonical Gospels.
But, along with this we can say this: the text is late, the orthodox Christians said The Gospel of Judas was nonsense, and the theology (which is clearly gnostic) is not 1st Century Jewish/Galilean. No one can dispute any of these three points."