Well, my plan worked almost as expected.
I didn't have to delete the existing AZ Topo first because, as expected, the new data overwrote it.
Also, MapSource couldn't "see" the micro SD card in my GPS unit (which is where I wanted the new maps to reside), so I took the card out of the unit, inserted it into a card reader, then MapSource recognized it and transferred the map data to it.
So I'm now "good to go".
Thanks again for your help!
LLOYD S
I didn't have to delete the existing AZ Topo first because, as expected, the new data overwrote it.
Also, MapSource couldn't "see" the micro SD card in my GPS unit (which is where I wanted the new maps to reside), so I took the card out of the unit, inserted it into a card reader, then MapSource recognized it and transferred the map data to it.
So I'm now "good to go".
Thanks again for your help!
LLOYD S