The steering gear can be adjusted. There is a locknut and worm gear adjustment screw on top of the steering box. What I've done is jack the front end of the truck up and get under the front of it to inspect play in the output shaft of the steering gearbox where the pitman arm is connected. If you push back and forth on the steering gearbox shaft and feel play, you can try to adjust the box to eliminate the slop. Loosen the locknut on top of the steering box and use an appropriately sized allen wrench to tighten the worm gear adjustment screw. This screw must not be turned in too tightly, only just enough to remove the pitman arm slop. Hold the adjustment screw in position and turn the locknut down to hold it in place. Now, let the truck down and take it for a test drive. If this doesn't fix your issue, then you will likely need to replace the steering box.

If you find that you need to replace the steering box, it's not too hard. The hardest part for me was removing the pitman arm (you will need a pitman arm puller to do this) and removal of the hoses (sometimes, they can be rusted on - use plenty of PB Blaster, along with a good flare nut wrench).