Way to go Bruce ! Congrats. You are in for a real treat.This is just my opinion but to drive the SDR around I would first try out a software package called SDR Console. It is free and has a very easy to learn curve. I have not checked to see if it is MAC compatible but I think it is.
As far as QRSS signals, the easiest quickest way to get up and running is to DL a free program called ARGO. It is written by Alberto and he is awesome as far as user requests and making sure the software is easy to use.
You will need a virtual audio cable to connect the audio output from the RSPdx to ARGO but there are free programs for that to. Let us know how you progress. 73 Gedas W8BYA