Try to learn everything about the "other" stuff involved with being a head director. Now you'll be dealing with students, assistants, admin, parents, other teachers, paperwork, scheduling, and anything else that will get thrown at you. Being head means you need to keep all your ducks in a row and be at least organized enough to handle all the stuff your assistants don't have to deal with (which usually is not no much difficult as just time-consuming and tedious).

Talk to anyone and everyone you can. It seems like you already have a good start with your mentor. Ask other directors how they work. If you're able, observe what they do and what their day is like. Get to know your future administrators. A principal that supports you can really help move things along when you need help.

Be prepared for backlash. I got the head spot when my HD was promoted. Even though the kids all knew me, I still got attitude from some (especially upper classmen) because I didn't do things the way he did.

My first year as head was rough. But each year afterwards got easier as everyone learned and adapted to the way I did things. I wasn't always right, but I tried to be approachable and open-minded.

This can be your hardest gig with so much to do, but it can also be your most rewarding. I wish you all the best!

p.s. Make sure to make some time for yourself. Your off time is YOURS. Don't let the gig consume you.