Are these conscious though? I always assumed faith was spontaneous. You don't just read a holy book and become a believer right? Faith stems from one's upbringing and/or deeply felt religious experiences. Whereas a non-religious book that gave you new facts about a particular topic could potentially convince you to change your mind.
I think you're right that opinions are harder to change the more fundamental to one's worldview they are.
1. Receiving and understanding new information
2. Processing and integrating that new information.
When the belief you are updating is a relatively unconnected node in the graph of beliefs, that second processing step takes almost no time. If it's heavily connected, the processing takes longer. That's why conversions often seem "spontaneous": your subconscious has been busily reworking the web of beliefs to integrate the new information, and eventually everything clicks into place and you have an epiphany.
I don't see faith as some special category of per se. To my mind, faith is simply another word for trust. The implication is simply that it is a belief you are willing to act on.
I think it is easier to change our beliefs about some things than others, but that has more to with how that belief relates to our other beliefs. If a particular belief is not just something we believe to be true, but is also a framework we use to make sense of the world, then new information is rarely sufficient to contradict it. With any worldview/religion/ideology, you're going to run into facts that are difficult to explain in light of it.