What's the most efficient way to get Livesplit up and running for Factorio? Is there a good guide anywhere?

There's not a good guide for LiveSplit at all, as far as I've found.

What I suggest is that you:

1. right-click > Edit Splits to build your own splits list. (Consider splitting on "builds" like your final Green Chip setup and avoid splitting on tech)
2. right-click > Edit Layout to get it to look how you want
3. Play with it to understand the various comparisons.
4. Use it to time a run -to completion-.

Then you should be good to go.

There is no Integration for Livesplit in Factorio, it's just an overlay in OBS. There are plenty of YouTube tutorials for livesplit in gengeral, just google for them.