Something doesn't sound right. This is fishy, how could he access your email, you are right in the fact your computer was accessed or used. If you did nothing in this, as in receiving the shipment and keeping it, I would go to the police and file a police report. The 5-10 years in jail is nothing but speculation. Your friend is probably not a lawyer or a judge. Cover yourself and file a police report, however if this goes anywhere you are going to have to explain how your computer was used.
Any charges will likely include potential wire fraud and other charges that may put this in federal court. However a $200 theft is not likely to land you in jail (which is for misdemeanor offenses), if a felony conviction hits you or your friend and incarceration is warranted - you would go to prison, not jail.
File a police report and cooperate - if you are involved do nothing and line-up a criminal defense attorney. Keep your mouth shut if arrested and immediately ask for an attorney, even if you don't have one.
I suspect, as usual there is a missing piece of information, because rarely have I seen a case where everything is disclosed. Beware of your friend, file a police report for identity theft if applicable. Remember, police only talk to you to build a case against you - their job is solving crimes not finding innocence. Also, be advised that police can lie to you with language like "your friend is next door "diming" you out, but you however cannot lie to them, because they are trained to detect misinformation and/or lies. If arrested, let a lawyer speak for you. Internet crimes are a growing area of law enforcement, if you think computers are anonymous you are mistaken.
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I agree with my colleague, but retain an attorney first. It sounds like any investigation will be helpful to you. But it is best to be protected by counsel whenever dealing with the police and possible charges.