God's name in the Old Testament IS Jehovah. It would be correct to call Him that. Jesus is our Savior and anything that we ask the Father in Jesus' name He will do.
I am working on the Trinity issue. I am not clear on the whole thing yet, but I am beginning to give it some credence. So, I pray to Jehovah, My Heavenly Father, and I pray in Jesus' name.
My pastor said that using God's name Jehovah is fine, that it is one of the names of God. He asked if it made things confusing to me and did it bring me closer to Him by using Jehovah as God's name. His only concern was that it could take me away from the true identity of God.
I also pray that I am confused as to the matter at the moment. I ask Him for guiding me to the right conclusion. So, I try using different terms to see what brings me closer to Him.
Hope that helps a little. I guess I am on the same journey to answering that one as you are!