First of all, we have proof Jesus existed, that he had post-death/resurrection followers, and that he was a moral teacher/rabbi at the time from Josephus. We also have one by him stating he worked miracles, but that piece of his work is disputed to this day.
Also, when checking the age of the Gospels, it would be a much wiser idea to check the age of their
sources, not them themselves. Obviously we cannot find, and therefore date, oral sources. But Mark is already one dated source, and is earlier than any other Gospel. John may have been a source for itself and Gnostic writings, but it is also plausible they have another source, either undiscovered written, oral, or one of the other Gnostic Gospels such as Judas or Thomas, which may be between 500 and 2000 years old. Q is a possibly existent source for what appeared in Matthew and Luke but not Mark, but we have not found, and therefore dated, that yet.
An example for the authenticity of the Gospels I like to use is the sweating of blood. (Luke 22:44) They didn’t know it was scientifically possible, and they regarded it as a miracle and wrote/passed it down. Unlike many other miracles, this is scientifically possible and likely. Every other myth that has miracles, outside of Christianity, has no or only one scientifically possible miracle, which is usually
very unlikely. However, here we have one that is both possible and likely. They didn’t know this would be revealed to be such 2000 years from then, as other wise they wouldn’t have written it down for two reasons:
*]They would know it wasn’t miraculous.
*]It would have been a sign of weakness on Jesus’ part.
So, I believe that is evidence for one miracle to be correct. Whilst it is only one, I still believe it to contribute to the authenticity of Luke (or Mark/Q) as a whole and all of the Gospels and Sources.
Finally, here is a link to a rather decent article about proving the resurrection:
leaderu.com/everystudent/easter/articles/josh2.html
Oh, and @Marc Anthony, I would like to read that book when it is published, and I hope for you to finish it. 