In case you haven't seen this, here's the link to Nick Carter's setup instructions:
I don't think you can hurt the lathe by lapping it, even if the previous owner already did so. Mine is still new in the box - the "assembled" version - and I can tell you the carriage is somewhat difficult to slide by hand. It's really tight to the bed, and there's no perceptible side play. The feed and crosslide knobs both have backlash, so I don't think you have anything to worry about.