Complex sentence: The Gospel of Judas is probably from no earlier than the second century, since it contains theology that is not represented before the second half of the second century, and since its introduction and epilogue assume the reader is familiar with the Canonical gospels.
Split into simpler sentences: The Gospel of Judas is probably from no earlier than the second century, since it contains late second theology. Also its introduction and epilogue assume the reader is familiar with the Canonical gospels.