As a prior service NCO who will be reclassifying to 13F, what can I expect from AIT, my first duty station, and the MOS as a whole?

Dig into ATP 3-09.30, since you'll be showing up already an NCO you'll have some catching up to do. While you're at AIT ask the instructors if they will teach you what you're going to need to know as a company FSNCO. As long as you have thick skin, can learn quick, and are physically fit you'll be alright. The job changes fairly significantly depending on the type of unit you support. FiST platoons that work with infantry have Observers whereas those that work with scouts don't. What you're garrison and field life will look like will vary based off who you work with, but it tends to be a lot of field time since you'll go out with the maneuver unit you support and with the FA unit you're actually in. It's a close knit community because we're kind of the bastard children of the maneuver and FA. If you get a FO slot, which you'll need as a SGT, then make sure to integrate into the platoon you work with. And do NOT let the PL use you as a RTO. Show them the assets you bring to the fight, so they actually use you.

I was a re-class too. You need to pay attention and learn everything you can because you can expect little mercy when you get to your unit. If you show up not knowing more than the joes fresh out of school you will get humiliated in front of everyone. I've seen it happen. Big mistake prior service makes is taking leave between school and unit and brain dumping everything they learned, then they get shown up by the boots that went straight to their station.

You need to make sure the instructors at AIT teach you properly. Unfortunately when I went through they just kinda assumed that all prior service could just kinda figure it out on their own. The result was we didn't get as much practice in as the boots. They stuck us in the back of the classroom and treated us as an afterthought while they focused on the boots. When everyone else is shooting in the sims be sure to follow along, compare their data to yours and try to predict where their shots will land.

I was AD the entire 7 years I was in. Became an actual FO as an E4. Unfortunately I never got promoted to E5, but that’s a story for another time. I did the job well. AIT teaches you, but nothing better than OJT. You’re new to the MOS, so ask questions. Talk to the E4’s and below. They know more than you think. Being in the field is the best place to learn. I’m sure technology has changed since I’ve been in, but the job’s still the same. I could probably still do it.