welcome to join kpv and koreader community
We maintain our documents in the wiki:
you can find out guide on build environment setup in the wiki. Also I would recommend you develop on Linux machine (even a VM will be very helpful).
As for Lua, no worry, most of the Koreader developers, me included, learn Lua halfway through hacking ;p
PS: we add gettext support to koreader recently, and it now shipped with Turkish and Chinese translation. If you want to start other translations, feel free to send request to https://www.transifex.com/projects/p/koreader/
EDIT: never mind, I missed some new replies and seems that luksurious already got the dev environment set up, great