Step Mom Not Properly Executing My Father’s Last Will And Testament.

HELP.!! We want to proceed with legal action but want to be better educated. So what is my next step after hearing step moms wants to sell the property and give proceeds to her biological grandkids. Whom have no genetic attachment to the property. In addition, she is unfit and living in filth, a 100% mental decline and my husband and i are the only ones in the position to deem her unfit as executor and get her in assisted living, for her safety!!! Animal excretions and fire hazards, as well as gambling and other easy money schemes. We want to get a lawyer….but not sure about the entire execution process. This just scrapes the surface but is the relevant information. TIA!