What advice do you have for someone reclassifying from 68C to 12N?

SPC Moore, feel free to message me and I will answer an specific questions about 12N AIT, I was an instructor there not long ago and have spent most of my career in construction. As far as advice, you'll spend a week on each piece of equipment with evaluations on a variety of operating tasks. You wont be an expert operator, but you should have a solid foundation of maintenance, safety and operations to build on when you get to your unit.

After you get through AIT, if I was you, I get into some correspondence courses. These will help you catch up with the other guys who've been there for a while. Don't be afraid to learn the mechanical part as well. There are a lot of good construction jobs in the Civilian world so dive in real deep.

Get used to the idea of Route Clearances. I have a 12N buddy and he stated his entire tour in Afghanistan was nothing but Route Clearance.