The switch was pretty easy. I ran out there for a couple of winters in the 1980's. If I recall after the turntable went in and the wye was pulled out, there were only 3 switches on the mainline - one in Lahaina and two at the other end.
The turntable not only turned the engine, but also was the "switch" to the run a round track to get the engine on the other end of the train. After they turned the engine and sent it back to the other end. The conductor lined the table back to the main track.
Most of the time....
I recall at least two times when the engine went out onto the table with the table aligned to the other track. Thankfully the heavy deck timbers kept it from turning into a "485 episode". Later they installed a block signal to let the engineer know the table was lined up. I guess looking ahead and paying attention when running wasn't good enough.