yeah seriously dress as nice as possible.
any time u need to sway a person in power who knows absolutely nothing about u personally and u only have a very small amount of time to do so, one must look their best.
The saying "u cant judge a book by its cover" does indeed hold true much of the time. However, in your case u most certainly will be judged on your appearance because they just dont have the time to get to know u as a person obviously. So they must rely on what evidence is provided and what they see and hear in that limited amount of time. Your physical appearance in a way is evidence.
Its equally important to be well spoken and to be able to answer their questions quickly and with out much hesitation. I hope u rehearsed what points u want to make many times over in your head.
good luck yo....not that i care
nah man in all seriousness i hope it goes well for u and i will send u some good vibes. In fact i already have. Keep us posted on the outcome yo!