Mercedes Benz repair: Power Steering Gearbox - ongoing, disconnected line, matter of pride

Question
Update on diagnosis for 1998 Mercedes S600.

I took the disconnected line coming out of the Power Steering Pump and had someone turn the wheels.  There was suction on the hose.  I took some Power Steering Fluid in a cup and submerged the end of the hose into it.  It pulled fluid (quite a bit 1/2 quart) and when I saw fluid coming out of the connection on the pump - I rehooked up the line (hoping that my problem was solved).  Turned the wheel - lock-to-lock a bunch times with engine off and engine on.....still is like there is no power steering at all.  Any idea what would cause the fluid not to be pulled from the tank?  What are the chances that something happened to the pump during the gear box change - since it was working fine prior to the swap?  Any other diagnostic suggestions as I really hate to take it to the dealer (matter of pride you know).

Thanks again as always for your suggestions.

Answer
The power steering pump should put out hundreds of pounds of pressure, going to the gearbox.
If the input hole of the new/used gearbox is plugged, it can blow the pump.

Danger:
Wear a full face shield, long sleeve shirt, and gloves to protect from the high pressure spray.
Fill the pump, prepare for a mess, loosen the pressure line going to gearbox 1/4 - 1/2 turn, have a helper start the engine for a few seconds.  There should be pressure oozing/spraying out, if there is not = BAD pump, if there is pressure = bad gearbox.

Clean up spilled oil.