1. You should be fine ordering online. The biggest difference between cables should be the amount of abuse they can take and the brand name.
2. DV already uses lossy compression (you should see how big it would be otherwise!), and I don't know of any way to do what you want because that's normally associated with capturing, which is not what you're doing.
3. You can get some good information from Doom9's DV forum (http://forum.doom9.org/forumdisplay.php?s=&forumid=59), but remember the more you learn, the more general digital video knowledge you'll need to have. You may end up learning as much as 2-3x as much general information as specific DV info. If you do find more sites or learn more, come back and share it with us. As you can see our DV forum is still in its infancy, which I intend to work on since I have a miniDV camera now.
When I have a little more time I intend to write a guide for miniDV to DVD, but for the moment I have my hands full with a couple of other guides. That's probably just as well since it means I'll know a little more when I get it done. If you have the money (probably around $500) I highly recommend Vegas Video for capturing and editing. I haven't worked with the program extensively because I can do similar things with freeware, but the interface is first rate and a friend of mine (who's not nearly as knowledgeable about digital video) managed to start using it in no time.
I buy all my stuff from pricegrabber.com where you can compare prices and see reviews of all items.
To compress your AVI there are so many tools and codecs to make it smaller but depends of what you want to do with your videos in future...I don't have dvd burner yet so i just convert to divx or mpeg2 files. Go to videohelp.com and learn easily
good luck
