It is true that a Muslim does not inherit from an unbeliever. Usâmah b. Zayd related that the Prophet (peace be upon him) said: “The Muslim does not inherit from the unbeliever and the unbeliever does not inherit from the Muslim.” [Sahîh al-Bukhârî(6383) and Sahîh Muslim (1614)].
However, that applies only to the fixed shares alloted to each relative by the Qur'an.
In this case, we are dealing with a bequest, since there is a written will from your father. Muslims and non-Muslims are free to make bequests to each other, and it is an excellent idea when Muslims have non-Muslim family to make bequests to them. In Islamic Law, up to a third of the estate can be set aside for bequests.
Therefore, you may receive up to one-third (33.33%)of your father's estate, since this is the maximum amount of a person’s estate that can be bequeathed to non-inheritors.
If the percentage your father wishes to give to you is in excess of this amount, then you will not be permitted to accept this excess without the express permission of the other inheritors, since it is their right.
And Allah knows best.