I was driving my 59 Apache home from work tonight and noticed that my steering wheel felt like it had a lot less resistance than normal, almost sloppy. I thought maybe the lash adjustment had backed out somehow. I checked it when I got home and the retaining nut was still tight. I loosened the nut and tried to tighten the adjustment screw a bit to see if there was any change so I would know if I needed to go through the adjustment procedure again tomorrow. The screw felt a little funny, but I made an adjustment and tightened the nut up again. I pulled down the driveway to see if it had any effect. It still felt wrong, almost worse. Thinking maybe I loosened it instead of tightening it, I tried again. I checked and I was going the right direction. I decided to roll down the driveway one more time. This time the steering got extremely sloppy and then I lost my ability to turn left. When turning left, the steering wheel keeps turning with little to no effect on the wheels. When turning right, it works, but definitely not correctly.
Anyway, this brings me to the important stuff. I'm assuming my gearbox is broken. I've checked online and found a supplier that has rebuilt ones in stock (most I saw were out of stock). I've also seen rebuild kits like this one:
http://www.classicparts.com/1955-59-Steering-Box-Rebuild-Kit/productinfo/76-912/#.WIK-fO8izIUTo me, this looks like it doesn't have everything I would need to fix as big of an issue as I think I have. A while ago I found these detailed instructions on rebuilding these boxes:
https://www.flickr.com/photos/advance-design_parts_co/8257853639/in/album-72157632210242370/I feel comfortable doing the work, but I'm afraid of having trouble finding all the parts required.
Anyway, I've always received great help here and wanted to get some advice from more experienced people.
-Does this sound like a gearbox gone bad to you?
-Is this something you think should be repaired or is a replacement a better option?
-Has anyone ever had this happen before?
This is my daily driver, so I'm anxious to get everything back to normal. I'm going to have to borrow my brother-in-law's spare vehicle in the meantime. Borrowing anything from your brother-in-law is always extra motivation.

Thanks so much. Your help is always appreciated.