I don't know much about New Age, except that for a couple of years when I was very young I used to listen to a lot of New Age music, but I didn't know anything about a philosophy behind the music. I still don't know anything about that.
I don't know if Tarja was connected to any of this, because after all it's Tuomas writing the lyrics. She probably had some esoteric beliefs, there was this Romanian healing man that she blindly trusted (it was mentioned in the band biography), but what else she was into is not very clear to me. Perhaps with her book coming out soon we will learn more about that side of her.
I don't know much about Tarot, and I wouldn't know where to start. If there was a "starter" album for them, which one would it be?