Make the most of your shadowing!
As someone who has gone through the above (years ago!) and with shares but with basic awareness of Codeco I would recommend you really make the most of your shadowing time.
Make sure you ask lots of questions while you're watching, if something doesn't make sense, ask! I also second that once you are sat DOING check in, it's so much easier than learning in the classroom so relax, it's all about to start falling into place!
Don't be afraid to jump in and start checking in, try and do at least one on your first day... seriously, the first is your hardest and it all gets easier from there, get stuck in! Also, while you're shadowing is the time to make a mistake - if your shadower is any good they will pick up on it before it's made, and if they don't it's their responsibility and not yours. Sounds harsh but it'll all make you a better agent.
Good luck and enjoy it! You really will wonder soon what you were worrying about :-)