Steering Box removal and installation

I'm changing the power steering gearbox in my 1976 dodge dart sport power steering gearbox. I have the old one out but have run into a couple of problems. 1. does the pitman arm need to be pressed onto the steering box shaft? 2. Does the steering column need to be unbolted and pulled back to align the steering linkage? I was trying to make things better an I am wondering if I should have left it all alone. LOL