We have almost no information about Jesus outside of the gospels, but by comparing the gospels to each other and apply critical reading and knowledge of the authors biases, we can make qualified guesses to how much is historical fact, and how much is myth and legends.

To take some examples: Was Jesus actually crucified? He probably was, based on this reasoning:

• It is described in all four gospels.
• It it a plausible event - crucifixion was the punishment for rebellion against the Romans, and naming someone the Messiah was basically an act of rebellion, since the Messiah was the one foretold to liberate the people from foreign oppression.
• It was a disappointing and embarrassing end, since the Messiah was expected to be a triumphant king. This means the authors of the Gospels did not have any theological incentive to make up such an event.

Now, compare this to the well known narratives around the birth of Jesus:

• Only two of the four Gospels (Luke and Mark) have any narrative around the birth and childhood of Jesus
• The two narratives are totally different and even contradictory.
• The authors had strong theological incentive to create the stories. It was prophecies that the Messiah should be born in Bethlehem, but Jesus was known to come from Nazareth. Both narratives tries to solve the problem of explaining how he came to be born in Bethlehem.
• The stories are historically implausible. The census in Luke does not correspond to any known census, and censuses did not happen like that. Herod killing all children in the country under the age of two is also pretty implausible.
• The stories uses literary tropes from other legendary accounts.

So evidence points to the birth-narratives being legends which have been created later.

Regarding the virgin-birth, there is good reason to believe it was a legend that originated some time after the death of Jesus, when Christianity spread to Greek-speaking communities. The reason being the virgin birth reference a prophecy by Isiah, which is different in Hebrew and in the Greek translation. The Hebrew text states that the Messiah will be born by a young woman. In the Greek this is translated as virgin. So only for the Greek-speaking communities is it really necessary with the story of a virgin birth in order to "prove" that Jesus was the Messiah.

I can't answer your question with any sort of detail. What I can give you is a link to this website: http://www.earlychristianwritings.com

After spending time on that site I feel like I've sat in on countless lectures on New Testament scholarship.

From the site's description: "Early Christian Writings is the most complete collection of Christian texts before the Council of Nicaea in 325 AD. The site provides translations and commentary for these sources, including the New Testament, Apocrypha, Gnostics, Church Fathers, and some non-Christian references."

The commentary for each section is taken from famous works by New Testament scholars through out history and gives great context on the historicity and theological development of each individual piece of Christian writing.