Certainly what the clergyman agreed to is important. I would also say that we would need to go back over the basic tenets and practices of our faith, having in mind arguments that Muslims might use against us. Many Orthodox in the west today are ready for Catholic and Protestant arguments, at least to the extent that we can come to a "draw" in an impromptu debate/discussion. But would we be able to answer a muslims charges?
Are we polytheists? If not, why not? Can we go beyond a simple "three persons/one essense" catch-phrase defense, and really get into a meaty and reasoned defense? What evidence can we provide that Jesus was and is God?
Are we immoral and immodest? If not, how do we explain how members of our own religion dress, act, etc. in public and private? How do we defend ourselves without judging and condemning our brothers and sisters in Christ?
Are we creation worshippers? Does bowing down before icons make us idolatrous? Are we familiar enough with the theology of Sts. Theodore the Studite, John of Damascus, et al. and the 7th Ecumenical Council to refute the Islamic charges?
Most importantly (on all three points and more), can we defend our positions using evidences that they will not automatically dismiss out of hand, but will at least give a listen to? Saying "the Bible says this" or "the Fathers say this" won't do much when debating a Muslim, as it will when debating a Protestant or Catholic. Personally, I know I am very unprepared for such debates.