I will leave further explanation of Theosis to others on here who are much wiser and better at explaining that sort of thing than I.
As to asking questions, you are welcome to ask questions here. That's a big part of what this forum is for. That said, talking to an Orthodox Priest face to face will be a better chance to ask in depth questions and to get authoritative answers. As to chatechism, there is not an "Official Orthodox Chatechism". Chatechesis is handled individually by each priest with each chatecumen. At some (usually big) churches they will have organized classes and materials that they use. Other times reading of books and writings of the Early Church Fathers will be combined with teaching by the priest and ongoing dialogue/discussion. Always it will come back to: "Talk to you Spiritual Father", which is to say the priest who will guide you in your spiritual journey through life. Usually this will be the priest at your home parish, but some have SF's at a monastery or a church they used to attend. Remember, you are welcome to feel at home here, and to ask any question you can think of.