How can we get our dads property if he didnt sign a will?

My dad died and his wife gets everything due to the fact his will was lost. They were going to divorce in 99 and she signed a quick claim deed in 99' that she didn't want anything but they stayed together afterward. She signed that and got a truck from my dad and lost it to her drug dealer before returning to my dad. The divorce didn't go through. My father died last Tuesday and she signed a notarized paper that was drawn up by a paralegal that she didn't want the land or house again the day after his death. She sold his tractor immediately after his death and is a drug addict ( to the point of near overdosing daily) she is already thinking she made a mistake by signing. It has been a week and she is almost out of money. What legally do we need to do to save our father's land and home for us his daughters. We have both signed notarized copies.