it definitely is authentic..it has been carbon-dated and it was written earlier than the new testament books like Mathew, Luke , Mark and John..
the reason it was neglected(if not hidden) by the Chrsitian Church(not just Catholic) today because it contradicts our perception of the Jesus we know..example of this is a child Jesus who zaps electric-like powers at birds and his fellow children..another is Jesus kissing Mary Magdalene(yup,made famous by Dan Brown's Da Vinci Code)..
so does it affect one's faith?..yes it does