What would be a good resource for learning Arabic - at least enough to get by in the Liturgy?
I find that for me personally, understanding, reading, and following along with the Liturgy in Arabic is much less challenging than reading classical Arabic works, the newspaper, or even the Bible in Arabic. This is mostly because the Liturgy uses much easier and less diverse vocabulary than these other works.
I would suggest familiarizing yourself with Liturgical terminology and prayers in Arabic. I also recommend buying a Liturgy book with Arabic on one side and an English translation on the other. You will have to learn the Arabic alphabet if you want to be able to read along and get the proper pronunciation down, it's really not that difficult. Also, listen to hymns and prayers in Arabic either in Church or on the Internet and then follow along with the written text as this will increase the speed of your reading.
Btw, do you have any background in Arabic at all or are you starting from scratch?