If you're a "Networking Newbie", that's a fairly ambitious project!
File Sharing between computers should be reasonably straightforward and I'd suggest getting that working first of all. Make sure all computers are in the same "Workgroup". To do this in the Mac, navigate in Finder's menus to "Go > Utilities > Directory Access". In the "Services" tab, select SMB/CFS and click the Configure button. Type in the Workgroup name. Then, in System Preferences, select the Sharing applet in the Internet & Network section and tick the boxes for "Personal File Sharing" and "Windows Sharing".
In the Windows PCs, set any folders that you want to have available over the network as "shared" by right clicking and selecting the Sharing & Security option [XP] or Share [Vista]. Ensure any firewall software is configured to allow access to the networked computers.
>>> share files on an external usb hard drive, print from one printer,
If the external USB drive is connected to a Windows PC, set it as "shared" in the same away as the shared folders.
If the printer is also connected to a Windows PC, then set it as shared too, but you will need to install Mac drivers for it in the Mac.
>>> access files on external hard drive remotely
By "remotely" do you mean over the internet? There is a fairly simple solution for doing that with the Windows PCs, but if the Mac is involved, it isn't so straightforward.
>>> if possible share photo and video files on TV via Sony Playstation 3.
As far as that's concerned, I haven't a clue!