Well I replaced the steering coupler AND adjusted out excess play in the steering box this weekend. Found no wear on the coupler at all -- I only wish that I new if the previous owner had changed it already. I think it's original but.....
Anyway, you have to remove two allen bolts on the coupler and the three mounting bolts for the steering box. If you try this, make sure that you mark the splines on the steering box shaft in a way that allows you to put the new couple back EXACTLY like the old one came off. You can also center your steering wheel if you have the time to play with it. Steering is noticeably tighter now. Worth the effort but it was tedious.