The slip you fill out changed a few years ago. Here is a link to the one you have to fill out now (at least, i think its still accurate).
It only asks about conviction history, history of deportation, and possession of firearms or drugs (in your baggage). I think you can truthfully declare no conviction, and not worry about tripping over the immigration system. I mean, if your record was expunged, you have no legal history of conviction.
If you have any documentation that supports the court order and any proceedings, you might take that paperwork with you in the highly unlikely event that this past event shows up on an immigration officer's screen.
Each case is different. Each officer's reaction has the potential to be different, so I wouldn't expect the consulate to give you a definitive answer. Your lawyer will probably hedge his answer too. But I don't think immigration is actively looking to catch people in technically paradoxical situations. I think you are likely to get responses that say, "Well...we don't know, so you will just have to go and be truthful on your declaration").
Anyway, that is my take.