score:9
The language has certainly changed. As such, translations into modern Greek are used.
Today's Greek Bible is often used, and translations by the Hellenic Bible Society have the Blessing and Approval of the Ecumenical Patriarchate, the Holy Synod of the Greek Church and the Patriarchates. There are other translations of the Bible into modern Greek, and it must be noted that the underlying manuscript(s) used vary just as they do in English translations, but perhaps more so because of Greek Orthodox distinctions. Going beyond this into the realm of what every Christian group in Greece prefers is too broad. Given that Eastern Orthodoxy is the predominant Greek religion, I've stuck to this.
The history of translating the Bible into modern Greek is fascinating and filled with lots of controversy, but such a review is beyond the scope of this answer. I refer you to this Wikipedia article for some additional context, but it is quite biased and often unsourced. The Greek version has a list of translations.
The type of Greek used in Divine Liturgy varies by jurisdiction and local conventions. Increasingly, Greek Orthodox churches use the predominant language of the country where services are held. Where Divine Liturgy is in Greek, it is often a mixture of modern and biblical (Koine) Greek (similar to how English-speaking churches retain some archaic English phrases in their liturgies).
Upvote:4
The majority of Greek-speaking Christians (Greece, Turkey, Cyprus and the diaspora) belong to the Orthodox Church. While some sectarians (i.e. non-Orthodox) may use some other text, to my knowledge the Greek New Testament text used within the Church is the 1904 Patriarchal Text. It is very close to the so-called "Majority Text". You can find the complete text online via the preceding link. I have never heard of any translation of the Koine text into "modern" Greek being used in any Orthodox Church.
The Old Testament text used by the Orthodox Church has been the version based on the Septuagint and includes all of the deuterocanonical books. The version commonly used in Greece is that published by the Apostoliki Diakonia.