I've done it a couple of times without any trouble. The seals install from the inside. You have to remove the cover on the back side of the box. Remove the sector shaft and you will find two seals. One facing out to keep out the dirt, and one facing in to hold in the oil. Mark the pitman arm before you remove it, and mark the sector shaft so you reinstall everything the same. There is an adjustment screw that sets the back lash for the the sector shaft gear teeth. You set that with a torque wrench. It's not really difficult, just be careful you don't make any mistakes.
are we talking about the same seal i believe the sector shaft is where the pitman are ataches to i am talking about where the steering column shaft attachs to box there is a plate where the two powers steering lines connect to that plate looks likeit just bolts on and slides off ?