1. Transmission, I believe, is the best torrent client under OS X.
2. Install ClickToFlash
http://clicktoflash.com/ and that should sort out problems (if you're using Safari).
3. Maximise your use... I'm not sure what you mean there, but I assume you mean "get the most out of it", and that depends on how you use it, and what you want to do with it. If you want to optimise and maintain your Mac, I suggest you take a look at OnyX or Cocktail.
As for the ethernet thing, that should work fine (if you need help just Google how to set up a internet-sharing ethernet connection), and maybe try toggling "Interference Robustness" under the AirPort menu item my G4 has it, so I assume yours does too.
i have done what all you've suggested.. now my problem is how i play the downloaded torrent movies.. quicktime player doesn't really plays it, and i tried updating it, but needs a 10.5 O.S.. maybe i need to update codecs?(used in windows, i don't know what it's called in macs).. a link to update my quicktime player would be nice..
or i just need to download another player? and what is it and where can i download it? thanks so much..