I can't speak to the (totally weird) insurance system you guys have got going on there.
But being nervous about your first appointment with a T? Totally normal! You don't know this person from a bar of soap, and you're there to get help with a very personal and traumatic situation. And you don't need to scan too many posts on this forum to have some idea that therapy isn't exactly a walk in the park.
So it's an incredibly important, but also an incredibly brave first step and you need to try and give yourself some kudos for that. It's a major stress, but it is absolutely the right thing to do.
As for what to expect? No fireworks! The first few appointments are more about building a relationship between you and your T. They need to get to know you and how you tick, and same goes for you getting comfortable with them. All the disasterously personal questions that you don't want to aswer? Not likely to be on the table unless your T is feeling like you're comfortable and ready to share. And if they ask something you don't want to talk about, it's perfectly ok to say so.
Your T will have had first appointments with plenty of clients before, and they will understand how stressful it is for you. Their goal is to make you feel safe, not terrified, and that's exactly what they're going to want to do at your first appointment.
If there's particular questions that you have, go ahead and write them down in advance to make sure you get the answers you need. After all, they're working for you!
This is a really great thing you're doing for yourself. It's ok to be nervous. It's also ok to be proud of yourself:)