You need to speak with a criminal defense attorney. You have the right to avoid making incriminating statements on a public website. If you have taken something you shouldn't have, it might be a good idea to give it back.
[In accordance with the Avvo community guidelines, this communication does not constitute "legal advice", nor does it form an attorney-client relationship.]
First off do not admit to committing a crime anywhere, especially on a public website. It can be used against you in a court of law. It is a good idea to speak in the hypothetical.
You need to speak with a criminal defense attorney immediately, and before you take any further action. You do not want to do or say anything that can incriminate you any further.
I am not offering legal advice and in no way does this post create an attorney-client relationship.
Contact a criminal defense attorney in your area immediately, many of whom will give you a free consultation. If you have already been charged, please ask your attorney for answers to these questions. Do not give anymore information out online - it is possible for a person to deduce your identity from what you say, and your words here could end up being used against you.
Doing anything at this point, if you have been charged, could be proof of guilt. If you havent been charged, and no one knows the laptop is missing, then it may make sense to get it out of pawn. If using the credit card for gas was improper usage, then it may make sense to let whoever pays the bill monthly know you used it with the intent of paying the amount used. Even if the school doesnt pursue criminal charges, you very likely could be terminated. Discuss all of this with an attorney as soon as possible.