What I'm understanding from your post, is that you would like to know, if you can connect the Slingbox to a TV and get the signal from the DVR located in a different spot without a connection to it.
In this case, for you to be able to get the Audio and Video Signal, you need to connect the Slingbox directly to the Set Top Box (DVR) to feed the signal that you can receive from the computer.
You can check the following link about the connections that you can make, besides that, the list of supported Audio and Video devices.
A slingbxo will work just fine conencted to his HD receiver in the manner he mentioned in order to vieew content from the dvr's in his household. Whole Home DVR service is DirecTV's method of streaming content from a dvr in the household to any other non dvr hd setop box in the household on the same network (either connected via ethernet, deca, wifi or powerline adapter).
He will retain all functionality as if he were at the non dvr hd receiver location.
In basic terms it will work just fine.