What Kind of lawyer do I need to settle a dispute over property that involves an estate and will?

Have paid the property taxes on a home my mother and step father asked us to buy because my brother had died and the piece is now theirs (?) (Property had been vacant since his death) My family and I moved in summer of 2010.A price was agreed upon, and then my step father appreciated what we had done to the home, because it was in bad shape when we moved in, and said he did not want the money we agreed on and to only pay half to my Mom. Nothing has ever been in writing, and now my step father has past away, but he left his wishes stated in his will. This is the only thing in writing and a lawyer filed the will. There is alot of tension now between my mother and me and she is threatening that I do not own half. I would like to buy the property and get it into my name legally . There have been many witnesses as to both of my parents expressing they were selling the home to me, but now we find out my brothers estate was never probated or settled and the property is still in his name