Hi Michael,
You can add a motorising unit later if you feel like it... and you will feel like it after you finish turning around your first loco by hand. It needs an awful lot of turns on that manual handle make it go through 360 degrees.
The first motorising unit I got was the Atlas geared drive... sheeese, the noise it makes!!!!! I think they have replaced it with a very quiet rubber drive (remind me to get one of those)
Wiring is simple for the motorising unit... use a double-pole-double-throw switch wired exactly like the direction switch for your locos and the feed wires to the motor are the same two that would have gone to the track. At present I operate my motorising unit with 3 volts just to keep the noise down.
All in all, the turntable is a work of art for it's price. I have had no operating probs with mine.
Hope this helps you.
Errol