If it's the free motion screw not entirely freeing up the movements I would start by taking off the stop motion screw and hand wheel; then oil all parts involved, both the turn axle the wheel goes one and inside the wheel. In my experience it often takes a bit of effort to get a machine running like new again, the best way about it is exactly what you have done; put it on a table, clean it up, detect all oil points and start to use the machine; keep on oiling diligently and tend to all the small issues turning up along the way.