Grant Of Probate

My father has a unregistered will, of my Grandfather witness by two unknown person,both the witness are alive and asking us to file the will in the court,My grandfather died in 1994. This will came in light in 2013,it was found in a old file condition of will is bad but readable.According to this will my grandfather given all his movable and immovable property to my father but many immovable property have already disposed off by my uncle. In 2013 when this will came into light all my uncles and aunties filed a property distribution case in the court. My father respond the case saying that my father has a last unregistered will of my grandfather but did not submitted the will in the court. My uncles and aunties replied in the court when we will submit the will in the court they will challange it. Now our advocate advise to my father to file a case probate of will. Please advise what we should do. The age of my father is 75 years.