Hi, I'm at work (in New Zealand, GMT + 12:00 + Daylight Saving) and forgot to have a look last night. I should have the spec posted here for you 9 hours after I've posted this message.

Yes, you loosen the nutslightly, torque the screw, and tighten the nut. All that is in the box is 2x worm gears running against each other at an angle, and the screw that you adjust push a ball bearing against the end of one of the shafts, which effectively determines how tight the 2 gears push against each other. Too tight and they will not move smoothly and eventually wear out the bearings, too loose and there will be play. Just make sure it is play in the box and not play in the pitman arm (steering mechanism pivit point) or ball joints (or loose mounting bolts...).

The adjustment should not go out by itself, but the nut might work itself loose just like the lock nuts on my twin carb throttle linkages... From what I remember the failure mode for the steering box is broken bearings, as it is unlikely that you will wear down the worm gear, but I might be totally wrong on this.