They are contained in the .dat archives (in FTL/resources/), though not all of them (some are hardcoded inside the .exe, I think, but that's a
pure guess on my part).
Essentially, you would be creating a mod - I'd direct you to
Mod Development forum and hang around there. As for tools, I'd recommend
Grognak's Mod Manager to load mods and
KuroSaru's FTL Dat Manager to unpack the archives (also to load mods, but GMM is slightly more widespread and easier to use).
Then, it's just a matter of translating blueprints.xml, autoBlueprints.xml, events.xml, etc files. Also images if you're ambitious.
