contest intestate

My parents divorced in 1992 in the divorce decree it states my father had to hold a 100,000 life policy on himself in my mothers name and also was to pay her alimony until she remarried or passed, she never remarried, my father passed away with no will( so the girlfriend says,now claiming common law wife) there also seems to be no life policy and my fathered owed her more than 40,000 in back alimony. The divorce decree states that if he has failed to comply with the decree she would be entitled to the funds first out of the estate. How do I go about contesting or putting this into evidence or whatever it would be called, me my sister and my fathers "common law wife " are the next of kin I guess you would say no letters have gone out yet for the court date to assign an executer. please any advise or help would be appreciated I am just trying to have a leg up before helping my mother proceed. thank you also we are in rhode island