You can do the pump from the top, but it's a PITA, you have to roll the engine forward, but it's doable. You can get to the line from underneath the car with the tire on. I can see the point of not changing the pump until you have the new rack, if something is throwing metal shavings around, you don't want to contaminate a new pump. Changing the lines seems a bit excessive though, I'd just flush them .