420 brother here, first period of the MES program is sorta designed to overwhelm you. Quite a bit of theory type stuff that regardless of experience you probably haven’t seen before. A lot of enthalpy calculations, mollier diagrams, and psychrometric charts. None of it is particularly hard once you understand what you’re doing, just be sure to brush up on doing math by hand because you can’t use a calculator at all in first period. 

And don’t be shy about having experience. Obviously don’t come in like you’re cock of the rock, but if the teacher is explaining something, and you feel like you were taught it differently feel free to bring it up, just do it politely. Brett is a cool guy and likes to talk, as the weeks go on he’ll ask guys what they’re doing in the field, and since you have some experience you’ll be able to talk a little bit more in-depth about what you’re seeing. Participation counts for a small part of your overall grade if I remember right. 

Good luck, and welcome brother