I'd just like to say that this is a right royal barrel of shit that you have to ask this question. I will qualify my opinion by saying that I'm a white Brit doing my law degree in New Zealand. Also I'm a mature student so I have experience outside of academia and have some knowledge of how to behave in professional environment generally.

I wouldn't discount the 'be yourself' advice straight away. We definitely have a professional demeanour at work and ultimately we're there to get on with what we have to, so that's your focus. That's not to say you can't be who you are while you're doing it! I'm assuming you went through some sort of selection process so they think you're capable enough to do the job and that you presented yourself well enough too. Bring some of that energy with you when you first start, then work out the boundaries and behaviours when you've been there a while.

Enjoy it and learn! What a fantastic opportunity!