I suggest hiring an attorney right away to challenge the will.
This answer should not be construed as creating an attorney-client relationship, and is for informational purposes only.
I agree with the other answering lawyers. You need a lawyer ASAP. Judges are concerned not only with what is the just outcome but judges are also bound by procedural rules that sometimes get in the way of justice so you may lose your chance to fix this problem without a lawyer. The story is told of a law student in a classroom arguing with his professor. The student says, "But that is not a just result." The professor tells the student to go outside and see what the building says and come back and report to the class. The student does so and reports that the building says, "School of Law" not "School of Justice." Procedural rules are very rigid in probate.
You need to hire an attorney immediately. Technically you are not challenging the 1989 will as that was a valid will when prepared and from your facts was not the product of fraud, duress, or undue influence. What you are doing is offering the more recent will for probate and asking the Court to add you as a Co-Executor. Absent proof that you step-father knew of the 2000 will and knowingly submitted the 1989 Will to the court instead the.general rule is that any distributions under the older will are valid therefore it is critical that you get the 2000 Will into the court as quickly as possible.
This answer was prepared for educational purposes only. By using this site you understand and agree that there is no attorney client relationship or confidentiality between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed attorney that practices in the subject area in your jurisdiction and with whom you have an attorney client relationship. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific factual or legal circumstance described in the question or omitted from the question.
I am an attorney in your area. You need to act quickly and get an attorney. Do not delay - you have options but you need to act.
This is not legal advice nor intended to create an attorney-client relationship. The information provided here is informational in nature only. This attorney may not be licensed in the jurisdiction which you have a question about so the answer could be only general in nature. Visit Steve Zelinger's website: http://www.stevenzelinger.com/