I would drain the oil in any gearboxes and clean up any grit and debris found in the gear boxes as well as possible. Then I would refill with a good quality oil that meets the mfr. recommendation. The oil that comes in the Asian machines I have messed with was some pretty awful stuff. Then make sure everything is cleaned of cosmoline, lubricated liberally to help flush any contaminants, and test all the fasteners and wire connections on the machine for tightness. Do not over tighten them or they might fail. Then I would run it without the gears and lead screw turning, starting at the lowest speed and gradually working up to full speed over several hours. Then I would lube the gears and feed shafts liberally and test the different feeds and threads, using each position of each lever, and run for a while in each position. Then get to work...