This will be the fun part, it's not complicated like building a house, so the headaches are minimal when you have a contractor doing the job for you.
You will be amazed how fast the red iron goes up. You will go from a concrete slab to all the red iron up in one day, I remember I left for work in the morning with just a slab and came home to an actual red iron structure.
Oh...... here is another BIG tip. If you bought your building from a building dealer like I did, DON'T buy your doors from them. Buy your doors from a local door business. That way, they cover all the doors, door tracks, and open/close equipment through their warranty. You will likely need them to install the doors and get them all setup for you anyway, most general contractors don't like messing with roll up shop doors and HD openers. It's just easier that way, if there is a problem in the future with a door you can call them and work directly with them, rather than getting the run around with "we can't warranty our work with customer supplied doors and equipment." kind of BS. That way, it's their doors, their labor, and their problem to get out and fix a jammed up door on a Friday afternoon. Don't ask how I know.