I’d like to address what you mentioned about justification and sanctification more from the perspective of someone who previously was Protestant, but I am at work now and have had a crazy week. I will try to do so soon. Suffice to say, there are some things that can be seen parallel and others that are different regarding those doctrines. However - from a Pentecostal perspective - it wasn’t a big jump for me in that subject once I understood the language and concepts used.
Regaeding attending the Church to learn - in Orthodoxy, our hymnography teaches our faith, as well as various other things. It is really important for learning the faith, especially since books, learning and questions only give you part of the overall faith (its more than just theology)
I certainly did a lot of research before stepping into the church, but I learned a lot as well once I started to attend. My process was reading a lot, asking questions here and to other Orthodox Christians, starting to attend catechism classes right as I started visiting the church (before I decided to become a catechumen), and then when Pascha (Easter) came, I knew for sure that it was where God wanted me to be. It still took a long time after that though, as the catechism is designed to ensure you understand the faith before committing to it.
If you look at the first few pages of TAW, you will see the I posted way a LONG time before I became Orthodox

it was a journey and still is a journey for me.