We will be unable to answer this, not only because it requires quite a lot of legal training, but because we would be prohibited by law from giving legal advice - the "unauthorized practice of law" (UPL), as they say in reference classes, patent / trademark workshops, etc. Legal and medical questions especially are in this category - we can only suggest possible places to look if you wish to educate yourself on probate law, inheritance laws, wills, etc.
A main point that even if some librarians have legal training, it is not likely they would be able to give a detailed answer here. So much depends on what state you live in - and above all, the detailed facts of your particular case.
If you do want to do a bit of reading in the law - before contacting an attorney (or maybe to help in talking with an attorney you already have), many states have links to their "annotated codes" or databases of state laws. The pattern would be to go into the state website, maybe with a web address such as www.ohio.gov or www.state.ny.us , and look under Legislative or Government Information. You can also check for a "site index" or "site map" that would link to their laws or state codes.
Alternately, you can simply do a web search such as: "inheritance laws" site:gov (about 400 hits in google), or something more specific such as probate wills contesting site:ca.us (about 30 hits). If you are near a large public library, you may have luck checking for books on wills, probate, law self-help books, and related sources. Some large academic libraries allow access to big legal databases, but license agreements are a bit dicey with those. Many will require you to have a current student ID to get into legal databases such as Lexis Academic or Westlaw, and many others will have a very stern warning "for academic research only", or something similar.
With unlimited time, possibly you could learn probate law, and successfully represent yourself in a court case, but there is no question this could take many hundreds if not many thousands of hours of serious study. It would seem that for most people, there is no realistic substitute for legal advice - or at least no substitute for studying under some good law professors, if you wanted to do this yourself.