If your executor will not communicate with you, how do you…

If your executor will not communicate with you, how do you find out how far along you are in probate? Once probate is complete is that the time to challenge the amounts that the executor has placed on certain assets? I have received word that the will is being challenged by two of the beneficieries for the total assets of the estate. The will names my sister and I as equal beneficieries as "stepchildren" which we are. My brother and step brother claim that because of a recent divorce between my mom and stepdad, that we are no longer stepchildren. (He was our dad since 1972 and still had relationship). Do I and my sister have to do something before probate is completed? Should we counter claim, and do we have to notify the courts if we intend and disputing their claim? The estate has a net value of aprox. 1 million and includes and running and lucrative business. The executor has currently put my step brother in charge and he has full access to business files, properties, etc. I need to know how to approach this without just charging up legal fees and also what information I am entitled to as a beneficiary at this given time. Your prompt reply would be much appreciated. Nicole