Your DUI conviction does not have anything to do with your eligibility for I-130 approval, because all that CIS is deciding is whether your family relationship is valid. However, whenever you fill our your applications for the consulate, you will be required to provide criminal history reports from everywhere you have lived. A single DUI should not prevent you from getting your green card, tho it will be up to the State Department to decide whether to admit you as a matter of discretion.
I think what your attorney did for you was plead you to the B count and get the A dismissed. This is basically a standard 1st with a 6 month class. You will be playing $390 + penalty assessment, court fines and fees (all that comes to $1,700) and 3 years standard informal probation.
A first time DUI will not affect your immigration case as it is not considered to be a crime of moral turpitude.
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