For an employment application, how do I answer, "Have you ever pleaded guilty, no contest or been convicted of a crime?

OUIL is a misdemeanor, under Michigan law, so if you were found guilty or entered a guilty plea, you would have to answer "yes."  If you're not sure (for example, if you think you might have been in some sort of first-offender diversion program), you should check with the court where this sentence was imposed, if you don't still have your paperwork from this event.  I would assume that this was a misdemeanor conviction, until and unless you have something solid that says otherwise.

You are taking the right approach here, because you should always be truthful on a job application.  Even if they don't check before hiring you, if the company finds out, even years later, that you made a false statement while applying for the job, it usually means immediate termination, and it's "for cause," which both delays or prevents you from getting unemployment, and a serious negative reference when you apply for other work.

You were issued a sentence.  At the end of the sentence were the charges dismissed? In other words was the dismissal conditioned upon the completion of the community service and probation?  Then you can answer that you did not plead anything.  I would do yourself a favor and check with the court in which you were sentenced and see what the "official" record states.  But I think that you would be ok to answer no on the application.  If one asks if you were "arrested" then you will have to answer yes.  So I would also consider having the arrest expunged.  Ask an attorney about helping. It can be complicated to do. Good luck.