Hi Dave To do a real floor refinish, you will have to sand to bare wood, removing all of the old finish. Only a floor drum sander will do it....and an edge sander. Trust me....as tempting as it is to try, avoid using a belt (even a 4X24) and random orbital sanders. I've tried and what you get are lots of slight imperfections in the floor contour that will jump out at you when you put finish on it and shine light across the floor :-(
Now, if the finish is good but has some superficial minor scratches and dulling, then a ROS is with a course and then fine paper is a good option....but don't take the finish off. This is what I did to my 1400 sq ft of hardwood after I pulled up the existing carpet. Then wiping it down with a damp clean rag, allowing it to dry and then applying 5 coats of a water based urethane gave me an excellent finish that has held up well.