Ok Im not gonna touch that screw lol
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I understand Ben's point, but honestly, you have to learn somewhere, he did, and I did as well, which also means you can. Steering boxes aren't ridiculously expensive, so if you mess up, you could always just buy another one. (just dont mess up!)
Just do you research, buy the parts kit, (Rockauto sells all the seals for cheap) and go to town. The downside of this, is that your truck might be down for a bit, so it isnt a popular option.
I agree with Ben that factory new boxes are the best.... all the others are remanned and they usually dont last as long. Growing up, my dad had an 87 burb 1500 4x4, it died at 215k and the gearbox was the factory one, and it was as stiff as the day it came off of the show room floor. But then again, most things arent made like they were back in the day.