If your dad wishes to sell the property inherited through will then he can sell the same on that basis only. no further execution is required. of he enjoys the property then again he can do so and no execution is required. what does he want. he can also execute further will to anyone on the basis of that will.
If you are in city then you may have to get probate from court. And if court grant probate in favour of your father then your father can sale the property. Appoint local advocate and show all property documents and will and consult with him.
Your grandfather executed a Will in the year 2005 and died in the year 2007. Now your father execute your grandfather Will. How will he execute your grandfather Will? Where did the property of Will situate? Your query requires some more clarity. There is no time limit to present the Will.