Thanks for the reply!
I had already visually checked the wire harness connector (appears to be connected to the switch), so the next step would be to trace the wiring for the radio (to see if the prior owner was correct as to when the heater blower stopped working) and/or heater power and look for any relationship. Again, hoping to do so without removing anything except maybe the radio, but if I do, I will certainly heed your advice regarding those tabs-good to know!
From what I can see from the floor area, the heater switch wiring goes directly into a larger harness and, so far, I've not found anything connecting the radio to this harness but have not yet found the power source for the radio. Will be digging deeper this weekend and keeping my fingers crossed that the problem is not at the blower itself, as it looks like a big job to get at!