Finally, an area where I can chip in and pass along some info.
The arm that comes out of the steering box is called a Pittman arm, it goes inside the box and has gear teeth that engage the sector shaft.
To adjust it, make sure your steering wheel and front wheels are straight forward.
There is a locknut (usually 5/8" or 11/16") on it and there is a threaded rod with a slot on the end passing up through said locknut.
Break the locknut loose and while holding the slot in the end of the threaded portion with a flat blade screwdriver, back off the locknut a couple turns. That should allow enough for adjustment unless it's REALLY out of whack.
Tighten the slotted part just until it stops, make sure the threads are clean so you don't get a false reading. Don't crank the screw as tight as you can. Hold the slot at that point with screwdriver and tighten the locknut. If it is screwed in too far, it will cause excessive pressure and wear on the sector shaft gears and your steering won't automatically return to straight ahead position when driving.
If you can't fix it with a hammer, it must be an electrical problem.
1978 Executive 29' class A MH that might be worth fixing up to drive and use. Three four wheel drives, an off grid rock house, some chainsaws, and a screwball cat.