The steering box is just a saginaw, I think, and is little, if any, different from what my old Chevy has. The kit I bought from napa or Big A years ago came with a very detailed little (and I mean fine-print) instruction sheet. The kit was very cheap and worked great. I replaced both seals.
It was a long time ago, but I seem to remember loosening the retaining nut and just turning the steering wheel a little with the engine on (?). The fluid pressure pushed the seal(s) out.
Leave the box bolted to the frame and the hoses connected to do this.
Someone please correct me if this is wrong. I'll bet one of the rebuild places would answer your question over the phone.