One God, One Will (Exodus 3:14; 1 Corinthians 8:4-6 (LD 8 COD Head 5 Article 1)

The doctrine of the Trinity is a rather confusing doctrine.  In fact, it is a doctrine that we will not fully grasp or understand as creatures possibly even during glory. So, if this doctrine is so difficult can we really know our God?  What is good about such a confusing doctrine?  What does this doctrine have to do with our redemption?  In other words, if we cannot understand this doctrine then why talk about it?  What does such a doctrine have to do with the doctrines of grace?