Upgrading Bind9 safely using portupgrade

[Rafael Barrera Oro]

Which is the best way to upgrade bind9 using portupgrade without setting
anything on fire?

I have two FreeBSDs which act as master and slave DNS (not installed by me),
should i upgrade both bind's before they can work again?

should i kill bind before upgrading?

I'm sorry if any of my questions has an obvoius answer but i really don't
know the first thing about FreeBSD and really want to get to know it better.

Thanks in advance

Rafael