Okay, take a deep breath and calm down. Court is scary but it is not some sort of hellgate waiting to take your soul. The fact that you're here asking these questions tells me you're smart enough to know what you don't know, which is a hell of a lot better than many people.
My first advice to you is this: GET A LAWYER. You can ask for a continuance or attempt to get a public defender; the PD will be overworked but skilled, a private lawyer is more expensive but more specialized in specific laws.
Alright, so court dressing etiquette. Slacks/nice pants, button down shirt, decent shoes is the general standard. Ideally, even if your clothes are "church-clothes" that is better than going in a ratty t-shirt and torn up jeans. The judge will be less friendly (generally speaking) to you not respecting the court; showing up slightly overdressed may not win favors but it won't look (to a reasonable judge) negative to you. Honestly, if you have the $ and you don't want to wear your "church clothes", run out to a Wal-Mart or Meijer or some 24-hour store that sells clothes and buy a nice pair of pants and a button shirt. If you cannot tonight, run out tomorrow morning.
Please note what I said above, if you say "church clothes" and it quite literally is like a priest robe or something crazy flamboyant, then go with your nicest shoes, pants and button-down shirt.
Ideally, you never want to speak with the police, you politely say you want to speak with an attorney before making a statement. No matter what. The police are not your friends, they are there to make a case against you. Do not fall for it, part of our training is to make you think we're on your side; we are not.
You should be given a chance to speak your side of things during the trial. If you do not have a lawyer (I imagine this charge qualifies for one), follow their advice or request a public defender. NEVER go before a court and judge without a lawyer unless it is absolutely necessary. Public defender's exist for a reason; that reason is people who cannot afford a lawyer.
This section is only relevant if you decide not to get a lawyer for some reason. THIS IS NOT LEGAL ADVICE, I AM NOT A LAWYER
During your speaking time, the judge may ask you some questions. You should emphasize your college, your (hopeful) lack of prior problems and any good things you can bring up (sports, school honors, work history, blah blah blah). Your license may still be taken away despite this as every jurisdiction is different and some judges have personal feelings on some issues. It sucks but that is life; you ostensibly knew the law, knew you were breaking it and knew the risks. It happens. If your life is put on hold, that is not the courts problem but the judge MAY be lenient upon you.
When addressing the Judge, "Your Honor" goes at the end of every sentence. "Sir"/"Ma'am" is acceptable but not the best; always do "Your Honor". Answer questions as succinctly as possible until circumstances suggest otherwise; "Yes Your Honor, No Your Honor" you get the picture.
For gods sake, follow the advice of your lawyer if you get one and for gods sake, stop driving this crazy. 25 mph over the limit is barely acceptable if you were driving a pregnant girl halfway through labor to the hospital and I mean that morally, you still are breaking the law. People who do this are the reason so many EMTs and police officers have nightmares.
TL;DR Wear your "church clothes" or your nicest clothing you own. Address the judge as Your Honor always, if not that then Sir/Ma'am is acceptable but not ideal. Be calm, polite and it'll be over with quickly. Tell the truth, be short and simple.
Good luck to you!