Solved at last...
Thanks for all who took time to read my question!
As I stated in the original posting, I am new to Fedora 19, 64-bit (having just switched from Ubuntu 64-bit after some two years...). I had never needed to deal with SELinux to any large degree and had never encountered the likes of firewalld before! It turns out that THAT was where my problem ultimately lay!
I only "stumbled on" the firewalld GUI setup by accident while sifting through the Fedora KDE4 menu, looking for anything that I thought might be helpful in solving my problem. When I ran it (the GUI interface app) I found it quite intuitive, and really didn't need any help in doing what I believed needed to be done with it to allow Samba to communicate through it. I decided to make the default ZONE "Home" at that time, and configured the ports for Samba in THAT zone. Once I had done so, I was able to communicate from any of the pc's on my LAN to my Fedora machine, and so I was pretty sure I had been successful in setting it up correctly. I was of course unable to communicate OUT from Fedora to the rest of my workgroup (thus, my posted question).
Here was where I made a small error! The NetworkManager in Ubuntu looks very similiar to that in Fedora w/KDE4 DTE. There is ONE MAJOR DIFFERENCE in the two versions - the Fedora version has a setting for the wired network called "Firewall zone" which I had NOTICED, but didn't think much of at the time. Now, later on, once I had "stumbled" on to firewalld's GUI app, I did not recall having even SEEN that setting! I of course never realized that in NetworkManager, the firewall zone was set to "Trusted" zone! And I had NOT made any modifications to that zone! Thus my problem...
Needless to say, once I had realized my mistake, and set the current firewall zone to "Home" within NetworkManager, Samba performed flawlessly!
Guess I need to hit the manuals for Fedora, eh?
But, you would think that, because you can SET the default zone in the firewalld GUI, that any apps. working with the firewall (such as Samba) would simply USE the selected default zone! Instead I need to both SET the default zone, and then tell Samba what zone I want it to use...(not entirely logical, and one step too many!). If Samba had indeed used the DEFAULT ZONE, I would have had the problem solved a day earlier... - sigh...