This question was posted in the wrong place.  It was posted in the Desktop forum and your question belongs in the Server forum. The power supplies in the 2950 ARE HOT-SWAPPABLE.  Just make sure you have the other PS connected to power before removing the one in question.  Make sure the status light is green on the one you are leaving in. We'll work on getting the post moved to the proper forum.
 Need to replace the power supply on a PowerEdge 2950 I want to know for sure if the PS is hot swappable. Very afraid of consequences of any mistake. Thanks
PowerEdge 2950 Power Supply replacement due to alarm