Can a DUI expungement eliminate my probation period and how difficult is it to expunge a DUI record?

No. You would have your driver's license suspended.

In California, DUIs remain on your DMV record for 10 years and cannot be expunged from your DMV record. The DUI convictions may be expunged from the court records, at the discretion of a judge, but can still be used as enhancements for future DUI filings and convictions. In addition, you cannot expunge your DUI until after you have completed probation. However, you may be able to file a motion with the court for early termination of probation. I suggest that you contact an experienced criminal defense attorney for a face-to-face consultation and give him/her all of the facts surrounding your situation. He/she would then be in a better position to analyze your case and advise you of your options.

You need to petition the court for an early termination of probation, a lawyer in your area can discuss the process, likelihood of getting a motion granted and the costs associated with the motion. My experience has been that if you are not on probation the armed services will allow you to enlist, expungement can be requested when probation has ended (either it has been ordered concluded early or the time runs) but it isn't necessary for a recruiter to allow you to enlist.