Congratulations on your up-coming ordination
I think there's a recording of the Divine Liturgy on the goarch.org website. You can also find the Greek text of the Liturgy there. I'd recommend just listening and reading along. It's just a case of memorisation and getting the pronuniation right.
If you want to actually learn the language, I'm not sure there are any books specifically on liturgical Greek. Jeremy Duff's Elements of NT Greek
and the Cambridge Reading
(Ancient) Greek: Grammar and Exercises
are both excellent.