I'll confess that I'm quite new to Linux in general, so please don't assume anything when answering.
I've been trying to find information online about this audio device. People generally claim that they got it working, but most of the chat about it was from 2007 and they make reference to things like FreeBoB which has now been superceeded by ffado.
They also refer to Jack. I think this is for internal routing of audio, which I don't currently need, afaik.
Mostly I just want to play audio out via this device. All my music creation software is done using Windows/Mac software for now.
I'm worried I'm going to break my system in my naivety, so any tips would be appreciated.
(Note, not enough reputation to tag as firewire)
First of all, good luck!
Your best bet is to take a look at the ffado.org entry for that specific interface. As well as the ffado.org FAQ and Manual.
It's also a really good idea to get onto ubuntuforums.org, in particular the Ubuntu Studio sub-forum. Questions get answered pretty rapidly there in my experience.
That said, it's certainly not a trivial affair to get a FireWire sound card working in Ubuntu. I've been trying for over three years, on and off, without luck. I have an M-Audio card mind you that ffado.org list as 'Reported to Work' as opposed to 'Full Support' as is the case for you.
You're right about JACK - for simple playback you won't need to use that utility.