[jabulon]

Hi Dave and welcome back! There is a nice technobabble section on this site (the section you posted this thread in) and here you may find a lot of answers to the questions you're having. Also there is a general faq section with a lot of info as well.
In short, yes you'll need a torrent client like BitTorrent to participate, the client used depends on the type of PC your have (windows/mac/linux) (again see faq). Forwarding ports (the firewall thingy) is expedient and highly recommended although not strictly necessary to be able to torrent. Here is some general information about being firewalled: Before posting about being firewalled... (and again the faq section might have the answer).

Re-seeding a show isn't that difficult either. I saw that the link you provided is a link to an inactive audio torrent, so that means you have to make a new torrent file and upload that to this site. Again see faq on this: Audio BitTorrent Seeding Guide