May I suggest that Christianity involves a huge step of faith, but not one that is located where most people intend it to be?
It is not at the beginning ("there might be a God, let's act as if there were and see what happens"), but at the heart, because there is one statement in the Christian faith which I suggest simply cannot be reasoned or argued. It must be taken on faith. And it stands at the very heart of things. That statement is:
"God is as he has revealed himself to be"
But then, we take something very similar on faith in every sincere relationship we have, don't we?