Difficult situation.
While you are required to disclose on your school application any previous DUIs, I'm not sure I'd tell the nursing school just yet. You could quietly complete the program.
By mentioning it, you risk being thrown out of the program on moral grounds, or hope to cooperate with the school and see if they will try to work with out. I'd tend to think they would discourage you from going any further.
You will need to disclose it to the State board of nursing when applying for your license. At this point, I'd do the required classes, probation ,etc. When it comes time to apply for a license, you'll have almost six months of "compliance" if you play your cards right.
If you can finish out your degree, I'd complete it and worry about licensure when it becomes an issue.
I would anticipate a problem on getting a license. Usually they decide on a case by case basis. Depending on where you want to work and in what capacity, you may be able to find employment using your RN license, just not doing bedside or handling narcotics.
You can find more resources on impaired nurses here:
http://www.nursefriendly.com/impaired/
Hope things work out for you.
Andrew Lopez, RN
http://www.nursefriendly.com