The simplest way to proceed is to contact a local probate attorney to determine if state law requires a person with a Will to present it for filing with the Court, whether or not a probate is going to be necessary. Most state's laws provide you must provide a Will to the court even if probate is not necessary. There is a reasonable chance that if your father and stepmother owned everything jointly or which named her as primary beneficiary there may be little or nothing that would pass under the terms of the Will (the only assets that pass under a Will are those that were titled in your father's name alone and which do not have a named benficiary). Good luck in this difficult situation.
Mr. Post is licensed to practice law in KS and MO. The response herein is not legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter within the question. Oftentimes the question does not include significant and important facts and timelines that if known could significantly change the reply unsuitable. Mr. Post strongly advises the questioner to confer with an attorney in their state in order to ensure proper advice is received.
I would second the suggestions in Mr. Post's excellent response.
In the event that the Will needs to be probated, you would be considered one of the interested parties, (whether you are inheriting anything or not), and you would be entitled to a copy of the Will and the initial probate documents. This fact makes it more likely that there were no assets to be probated. In other words, everything was held jointly with the surviving spouse, or she was named as the beneficiary of such assets.
If the situation is as you suggest: the wife is not named in the Will and plans to contest it, then she will not have any access to probate assets, unless and until she files the Will and makes such a challenge in court. In that case, you would receive notification of these proceedings.
You might also wish to check with the county probate court where your father resided to make sure that he did not file the Will with them for safekeeping.
Best of luck to you and your family!