Stamp duty on the probate granted

A plot was won by my uncle in the DDA draw in 1987. Before his death, my uncle prepared a will for the same in the favour of my mother. The plot was allotted to my uncle after his death. On approaching the DDA, my mother was told that the will is unattested and it will have to be probated by a court. Recently we went to court and , on the basis of the will, got the judgement of probabte in my mother's favour. I have been told that 3% or 4% of the present value of the property (as per the evaluation ordered by the court itself) will be payable as stamp duty which I will have to pay one month from the date of judgement. My queries are as follows and will be helpful if any person of legal acumen and experience could help me. Do we really have to pay stamp duty considering that it is not a purchase but only a transfer within the family? Would stamp duty be done at the earlier rate (money that my uncle paid to the DDA) or the present evaluation? What is the present rate in Delhi for such stamp duty? Any relaxation for women? When will we get the probate letter? What all except probate letter do we have to present to the DDA?