Like a lot of people, I suspect, I have changed a steering box on a Disco. Unlike most, I made every mistake possible, and turned a relatively simple job into a right clown of a job.
If your going to change it, which you may well have to do at some point, don't tighten anything up until everything is on. I seem to remember the one pipe is a proper swine to get threaded in, and very easy to cross thread. (Although I did manage not to cross thread it).