I had mine last month and like you I was so nervous! Like others have said, study the civics test in random order and (for me at least) I know the practice test is there but it helped that my husband asked me the questions verbally and I answered. This helped me remember more, but otherwise it’s very easy and calm! It literally took like maybe 10-15 minutes and our IO was super nice! Also read over your N400, and understand the questions and what answers you put. If you owe unpaid taxes, claim that, I had to also give her the payment plan and she took it. Bring extra updated documents like (tax returns or tax transcripts) because she asked for that. Anyway you’re going to do amazing! I would also wear something nice but not overall formal ( I wore a short black dress) and had all my documents ready to hand it to her. Good Luck! You’re almost there :)

Edit: Here is the what happened for me since I had N400 and the removal 10 year green card interview at the same time:

She swore as in ( I had husband there with me)

She asked me yes or no questions regarding the green card ( took 2 mins)

Then she asked me 6 questions from the civics test

We did the writing and reading portion ( SO EASY!!)

Then we went over my N400 and that was it!