You should either complete the 100 hours in the time you were given or talk to your attorney to have the matter brought back to court for an extension of time. Do not rely on the clerk saying "Don't worry about it". When you complete the 100 hours, the organization you do it with should send a letter to the court saying that the 100 hours of community service is complete. If the organization doesn't do that, a warrant could issue for your arrest, and you d be violated, spend up to 15 days in jail.
This is not a big problem in most courts but how you handle it it depends upon where the court is located. In New York City you need to go into the compliance part before your deadline and explain to the clerk that you need more time to finish your hours. They will grant it to you and if they do not give you an extension, you must have your lawyer contact the judge and request more time explaining that the compliance clerk is not granting more time and you are a full time student. In upstate New York call the court and tell them you need more time and they will usually extend it. Most courts are also very flexible as to how much time you need and where you may complete your community service so long as it is with a not-for-profit and you can get confirmation of completion in writing on the company's letterhead.
It depends on what was told to you by the judge at the time of the plea since it sounds like you got a great deal reducing a felony to a violation. Usually, you can go to court with proof of how many hours that you have completed, explain your circumstances and you will get additional time. If the judge was adamant that the C/S had to be completed by a specific date or X,Y and Z was going to happen, he may be less accomodating and can sentence you up to 15 days jail for violating the terms of your conditional discharge; or any other consequence that the judge warned you of.
All answers are for information purposes only. Answering this question or any future questions does not form any attorney-client relationship. Be mindful, that answers are limited by the limited facts presented by the questioner and are not meant to take the place of competent legal advice by an attorney fully informed of all the facts surrounding your case. However, be aware that nothing posted in a public forum such as this can be deemed confidential or privileged communication. For a privileged private consultation, contact me at 212-385-8600 or via my website www.southardlaw.com
Never ever rely on a clerk. Each case is unique. Ultimately, you are the one who be spending time in jail if you do not own up to your promise to the court-therefore take responsibility and do not assume anything.
My advice is for you to do as much community service as you can and ask the judge for more time. As long as you show a good faith effort, the court should grant you an extension. However, if you are granted an extension and do not keep your word again bring a toothbrush when the judge remands you.