Probation of will

My father purchased a property in Delhi on lease from L&DO . After he died , the property was transfered to my mother through relinquished deed as all legal heirs 4 son and 3 daughters had given NOC for the transfer of property . Before my mother died she left a registered will making me the beneficier of the said property . I approached L&DO to get the property transfered in my name however they refused stating they would need NOC from all other legal heirs ( my brothers and sisters not ready to give NOC) or a probate order from court . I went to registrar to get a certified copy of the will but they could not find it . they have given in writing that the cant find the will but it is registered with them. But i have the original will . Out of the 2 witness , 1 is not available as he was the person who made the will and the second witness is available but he is very old now . I have possesion of the property as my mother was living with me till she died . Shall i go for filling a probate case in court considering no certified copy is available and only one witness is available . How much time this case would go on How much money will be needed for this court case .