Winding up the estate according to an unislamic will

Q: What should be done if a person dies with an un-Islamic will? The will specifies its own heirs and the shares for each person with no Islamic principles adopted. Non-heirs, according to Islam, are included also. What should be done in this case?

What about the the 1/3 available for bequest. Can the Islamic heirs agree on how to distribute this on their own through mutual agreement?

Making the entire upper floor a masjid without having a sehen

Q: Insha Allah, our masjid will be doing some extensions. We will be extending by putting an upper floor. I wanted to find out, if the ground floor has a masjid and a sehen, is it permissible for us to make the entire upper floor a masjid without having a sehen?

For example, if the bottom floor is 500 square meters (300 sqm is the masjid and 200 sqm sehen). Can we make the entire upper floor (500 sqm) masjid?