I-90 green card renewal after Nolle Prosequi

[Jauniba]

My husband's green card (which was a ten year green card) expires in October. He was arrested last year for getting super drunk and behaving badly. We hired an immigration attorney at the time to make sure that none of this would affect him immigration status. He got a pre-trial diversion (we're in FL) and now has a document that states Nolle Prosequi. The immi attorney told me to mail the arrest record and that Nolle Prosequi document in with form I-90. The attorney said none of this stuff should keep him from getting a green card and I should go ahead and stick it in there now and make them all aware of it because we have nothing to hide. But how do we "introduce" this in the packet of information sent to USCIS?  But I feel like maybe there should be an explanation or something?? If so, where would I write it? On the page for additional information? Also, wouldn't this come up later anyhow when they do the background check? Thank you.