The only thing that's different in a distributed cluster is the implementations of steps 1 and 6. As voidmain said, the details of that are not trivial, ESPECIALLY the details of how it never produces wrong answers during fault conditions.
I don't know that there's been an exhaustive writeup of that part, but maybe one of us or somebody on the Apple team will put something together. It probably won't fit in an HN comment though!
Or... maybe this is the part where I point out that the product is now open-source, and invite you to read the (mostly very well commented) code. :-)