I can drive a car, as I've said, without understanding precisely how an internal combustion engine works. I do need to know how to turn the engine on, how to steer and brake, the traffic laws and the fact that my car needs gasoline and periodic maintenance to keep it running. Some people have a desire to learn more and fortunately there are books and websites that will let you get into the details.
The essentials of what we Christians believe are in the creeds. These in turn are distilled from the Bible. But even the Bible doesn't explain everything. It tells us that Jesus died to save us from our sins but it doesn't explain precisely how that works. It tells us God exists but doesn't lay down philosophical arguments for his existence. And so when Christian beliefs were attacked, men and women who had philosophical talents often rose to the challenge of defending them with reason. One such person was St. Anselm, a Benedictine monk who was made Archbishop of Canterbury.
I'm not going to do an exposition of his ontological proof of God or his satisfaction theory of the atonement. But they were landmarks in the history of theology and serious theologians must study and consider them even if they disagree with them. And that's important in theology. The creeds give us the bare bone facts that we affirm; theology is the explanations we develop that help us see such things as reasonable to ourselves and others. But theology is generated by humans and it can be fallible. Even in science there is a difference between data and the interpretation of the data. As science progresses, old interpretations of what is going on may be superseded by newer and better interpretations. And the same thing happens in theology.
I myself, as a nurse, have found medical analogies useful in explaining how spiritual things work. Why for instance did Jesus have to die to save us? In scripture there are a lot of references to our need to have a change of heart. In Ezekiel God talks of taking out our hearts of stone and replacing them with hearts of flesh. So what if we think of Jesus has our heart donor? If you have congestive heart failure, the only cure that we presently have is a heart transplant. For that, of course, the donor must die. If our spiritual healing is at all analogous to the way physical healing works, then the idea that the donor of our new life must himself die is a useful metaphor. But if this approach doesn't help you, drop it.
And remember: saying something is a metaphor doesn't mean it's not true; it means you are using a picture to give insight about something that is real but hard to grasp. Those pictures of atoms, looking like planets being orbited by moons, that we see in science textbooks are not really what atoms are like. They are the artist's best attempt to depict something impossible to see with the eye and very difficult to conceptualize.
We cannot and will not know how everything we encounter in this life works. Scientists can't even figure out how consciousness works. How can I be the same person I was at 8 years old when every cell in my body has died and been replaced many times over? Yet you and I remain uniquely ourselves. We get bigger, we grow hair in places that previously had none, our voices get deeper, we get stronger, and then we get wrinkles, we get weaker, we shrink a bit but our loved ones don't say “you are at all not the same person.” Even if our opinions change, our quirks, our sense of humor, our love of certain subjects or hobbies or things in this world persist. We change yet we stay consistently ourselves. We are a paradox. Why do we expect God to be easier to understand than we are?
You don't have to understand everything about a fact to believe it. More importantly you don't have to understand everything about a person to love them. But if you love someone, you want to learn everything you can about them anyway. And if you love God, you want to understand whatever you possibly can about him. Just be prepared to be surprised by him—continually. And never assume you know it all.