Surely I need to have faith that the 'teachings' are indeed Jesus' teaching and not the teachings of someone else?
Yes. There are many different versions of the Bible.
The most popular one in America is KJV, but mostly because it is a protestant Bible. Catholics of Course use the Catholic Bible. And there are older Bibles, such as the 1411 Bible. In the modern age we have the New International One, the Jeffersonian Bible, the book Of Mormon, and the Conservative Bible.
In each of these Bibles the language is changed to reflect the beliefs of its writers.
For example (this is just an arbitrary choice) of how a verse can be change to reflect the beliefs of the writers:
KJV
Acts 2:1 - 'And when the day of Pentecost was fully come, they were all with one accord in one place.'
NIV
Acts 2:1 - 'When the day of Pentecost came, they were all together in one place.'
Now you'd think there was not much of a difference between the versus, but there is one difference. The word accord is missing in the NIV version, and that changes the meaning of the entire verse.
According to Webster's dictionary, the word accord means to bring into agreement.
So, without the word accord in the NIV version, that would mean that they were not in agreement with each other. That changes the entire message, does it not?
So if it were truly the words of Jesus, why would there be different versions of the verse and the Bible?
If God were all powerful and omnipotent, why would he allow these kinds of variations and interpretations of his words? It seems to me that it would be simpler to keep the Bible to only one version and make it very clear to everybody so that there would be no misunderstandings and misuses of the Bible. OR ELSE!
So you see, a lot of faith is needed to accept the Bible is of the word of God.