how would i replace this/assembly it?

Were you able to figure it out?

You have to get the bolts loose on the pump, I think they are under the pulley (holes through it) and on the back. Been a long time since I pulled it. Not hard, just loosen them and move down. You will need a pry bar to tighten properly, else they squeal, Olds PS pumps love to squeal. I don't know if there isn't enough belt surface area or what.