First, congrats, I know this has been a long time coming, and am sending good vibes your way. I'm from NM, and I echo what has been said above. I think they will expect you to project a professional image, but also to project yourself to some extent. So, wear something that is comfortable but professional. I think I've seen one provider in heels, all the others wear shoes that are dressy but flats. I'm a guy, so as far as makeup goes, I would say don't go overboard, if you wear alot of makeup, then that's probably appropriate for you, if you normally don't wear any, than maybe what you would wear to a special occasion, but not a ton.
A feel for the state, as was mentioned above, NM is very outdoorsy. So after they get hired, I've seen providers in suits to shorts and a tee shirt doing rounding. Several wear jeans at my facility. Another facility I work at does not allow jeans, but pretty much anything else goes there. You will find the smaller the town, the less dressed up the dress code. Albuquerque, Las Cruces, Santa Fe probably more dressed up than out here in the remote small towns.
As for your personal appearance, you won't be the only person as wide as you are tall, I can almost guarantee it. That doesn't mean that you can't find something that makes you feel proud and happy. Remember, you graduated, passed your boards, and are a APRN, not many can say that. You are someone they want to interview, and you are special. Remind yourself of those things when you look in the mirror in the morning and every time you take a break during the day. Remind yourself that you are worthy of this interview and they were in the same place you are now at one point.