in hindsight....
i would use a fluid transfer tool to remove most of the fluid from the pump reservoir
then i would disconnect the lines from the power steering pump (will still be a bit messy)
remove the power steering box and drain the lines as they come down - swap lines to new box and put it back together in reverse
when you refil the reservoir, jack up the front end and move the steering left to right filling the reservoir as you go. after about 10 - 15 times left and right, you can start the motor and fill it and turn it again if it needs
there are things needed to pay attention to like steering wheel / pitman arm centering.
if you just drop the box, the one line to the reservoir can break the plastic connection. if it is hard to remove that line, just cut it at the connection as there is extra line to play with.
hope this helps a little.