Sorry to hear about your Other Than Honorable/Non Judicial Punishment discharge in 2000. It is worth pursuing a correction to the records if you have the missing documents in your possession. You may be able to find some "pro bono" (free) or low cost legal assistance locally by contacting your state bar association's office or Legal Aid Society for a referral or by asking around at your local law school. They often offer assistance/advice to folks who can not pay. However, it sounds like you may need the assistance of a former military Judge Advocate General (JAG) or someone who is a specialist in military law, administrative records review and procedures from whatever branch of the military you were discharged in 2000. Getting that legal help may cost you now, but having a cleaner military record will bring better employment opportunities in the future. Good Luck, thanks for your service, and hopefully you've learned from that mistake.
This is a general comment to your posting and is not meant to constitute legal opinion or advice. This posting does not establish an attorney-client relationship in this matter. If you think you need legal advice or representation for this matter, you should consult a licensed attorney in your jurisdiction.