How should I dress for an interview?

Hey ask mechanics, I am a first year apprentice at a big leasing company. I have an interview coming up for a much better position and have a few questions.

1. What should I wear? A suit feels like overkill, so I was thinking nice slacks and a collar shirt.

2. I have long (ish) curly hair. About ear length and maybe down to my chin if I stretch out the strands. I love my hair but would cut it if it improves my chances. Should I get a clean cut for the interview?

3. I have enough experience for the role they’re hiring, but I am still relatively new to being a technician. How do I go about asking the shop supervisor about mentorship? I want to explain that I am keen to learn and ask questions, and also set the expectation that while I will be valuable I will also need some training.

Thanks for your advice!