Hi
What package will I need to install on the raspberry Pi? (e.g. runeaudio UI, or anything else instead?)
RuneAudio can't be installed by packages, it is only available as downloadable image (see documentation).
Will a USB DAC take installation to work on the raspberry Pi? If so, How do I do it?
No, nearly all USB DACs (Audio Class 2.0 compliant) should work out of the box.
How could I make a network on the raspberry Pi that I could connect to on my phone and use to control the runeaudio installed on it?
It is possible to turn your pi into an access point, but this needs some linux knowledge.
Please search the forum for "hostapd" and read
this.
This feature is on the roadmap and will come with one of the next releases.
Frank