He talks a lot about how the early Christians didn't agree with one another and there were several Christian belief systems because of this, and he also talks about how the apostles didn't necessarily agree with one another as well. I don't really believe that.
Anyway, as a Christian is it a bad thing to take this class that is based on the writings of a man who fell away from the faith and may have skewed writings? Would this be a stumbling block to my faith or could it be an "educational experience"? Advice needed! Thank you!
It is not necessarily a bad idea to take the class as long as you are willing to spend some serious time looking at countervailing scholarship. I regularly read or engage with material that pushes back on my worldview assumptions in order to be more thoughtful, grounded and articulate in how I share the good news of Jesus, the anointed king of everything.
If you do take the class, I recommend reading Andreas Kostenberger's book,
The Heresy of Orthodoxy: How Contemporary Culture's Fascination with Diversity Has Reshaped Our Understanding of Early Christianity. Kostenberger's thoughtful scholarship addresses specifically the ideas of "multiple Christianities" in the first centuries.
Additionally, books by Dan Wallace, Richard F. Bauckman, Craig Blomberg, Mike Licona, Craig Evans, and Gary Habermas are clear, scholarly works that unflinchingly engage with liberal scholarship. There are many gifts that come to Christians through scholars, even those who are not Christians, and even those who are not friendly toward Christianity.
As to whether taking the class will shake your faith, I don't know your situation or how the curriculum might impact your worldview so I can't speak directly to that. I will note however that "shaking" isn't always bad. Some of the times when secular scholars or critics "shook" me, I had to examine what my presuppositions were about my Christian faith. Setting aside the reality of particular, historical truths that Christians affirm, "faith" is not primarily "affirmation of a specific set of claims", but personal trust in the Divine Son, sent by the Father, in the power of the Spirit to complete his promised rescue and renewal. If someone told me that some of my beliefs about my wife's childhood memories were wrong, that does nothing to undermine my relationship to my wife.
Hebrews 11:6 indicates that faith (i.e. personal trust) is essential because no relationship can exists without it. The same is true with Yahweh, the God of the Bible, because if you are going to relate you first have to believe He is there (exists) and that attempting to know Him is a fruitful endeavor (those who seek Him are rewarded). If He is who He says he is in his self-sharing (Hebrews 1:1-2) then He is capable of preserving that self-revelation over time (scripture), capable of reassuring us when we doubt or are confused (see Thomas), and capable of initiating relationship with the most vile and hard-hearted sinner (see
Chapter XXIV of Tokichi Ishii's testimony). Since secular scholarship is largely materialistic, the continuing active role of Yahweh (John 3:5-8, John 6:65-68) in the world is ignored or hidden in favor of ideas about social movements, economic pressures, national identity, etc. But all of that is meaningless if the Divine Community of Three is actively bringing people into life-giving relationship.