You should consult with an immigration attorney because laws change all the time. You should also consult with an expert DUI attorney because you don't have to plead guilty. You may have a defense to the DUI. Most immigration and criminal attorneys will do a free consultation with you so it wont cost you anything.
A single misdemeanor DUI has no immigration consequences. You should be aware though that multiple DUIs may indicate alcoholism which is a bar to admission and may keep you from renewing or upgrading status.
A first-offense misdemeanor DUI won't have any direct immigration consequences for a legal permanent resident. However, as long as an LPR is on probation [even informal, court probation] he or she cannot become a naturalized citizen of the US.
Law Office of Lamar Peckham
555 Sebastopol Rd., Ste. C
Santa Rosa, CA 95407