I'd figure out exactly where the supposed play in it is coming from before I started throwing expensive parts at it. Steering boxes rarely just wear out (but sometimes they leak).

I'd probably have someone turn the wheel back and forth while watching all the parts move and/or feeling them/turning them by hand and feeling for play, kinda like you would for a u-joint. Same thing at the steering box- unlock the wheel and turn the input to the box by hand and feel if there is any play between the input and output.

If its just a "feeling" of looseness in the steering while driving, then it could even be an alignment or tire issue. Or even wheel bearings.