Van feels like it is randomly running over rocks, giving off a popping or knocking

Hello,

Sorry to hear about your issue there. What exactly did you have changed/repaired regarding the power steering? To me it sounds like they may have left something lose. You may want to bring it back to the shop that did the work and have them recheck everything.
That could be a safety issue, especially if they left Lugnuts loose of some major part of the steering components. If something were to come apart while you were driving, you could be in big trouble. Imagine being on the highway and a tire falls off.... It does happen.
If a mechanic is rushing to get a job done and forgets to double check his work.
I wouldn't take this issue lightly, bring it back immediately. They are responsible for any damages etc. Don't risk your safety.

Receipt states - They replaced rack and pinion steering gear assy. Refilled system set toe in. They also replaced studs and nuts.

I would still recommend bringing it back if it does not feel right, with all those parts replaced you should have a nice smooth ride. There is a number of things that could have been left loose on a job like that. They need to fix whatever is wrong, if it wasn't doing that before you brought it there, you need to bring it back. Please don't risk your own safety.