Steering questions

[1979C20]

When I got my truck my steering box leaked at the rag joint and eventually got so bad that it leak all of the fluid out in about a mile or 2. So I got one off craigslist for 40 bucks and installed it about 8 montgs ago. It leak from the rag joint, just not as bad(yet). But when I anstalled this box, it made my truck pull to the left, and when going straight or around a slight right hand curve when the wheel is 3/4 of a turn to the right, the truck shakes pretty bad. It seems like a tooth is missing in the gears in the box. If I barely turn the wheel to keep the truck in the lane it  goes farther right, then back, then right, then back, untill I come out of the turn. Its extremely dangerous and I was wondering what it could be and how to fix it other than replacing the box, because a reman box is 130 or something like that. Also, how hard would it be to replace the seal where the rag joint goes so I can put my old steering box back in.

[RCCoors]

The input shaft seal isn't that hard to change. The most important thing to concern yourself is to mark the position on the large outer nut and the inner shaft nut. Make marriage marks before doing anything and you should be alright. I found several videos on you-tube as well as the instructions for references. It's really important that they are put back the same way they were as it will change the play in the wheel if you don't. Hope this helps and good luck with your steering box.