http://www.apple.com/quicktime/buy/
$30 to go from standard (free) edition to pro (paid) edition. The code they give you is only good for the current major version. Right now, the codes for Quicktime 6.0-current is what you'd pay for, but when 7.0 comes out, you would have to pay again to get a code that unlocks all the features.
Not worth it in my opinion, I don't have much content that I'd watch on my PDA that started in quicktime format. It just depends how many movie trailers that you want to copy over, I think.
In the meantime, a simple google seach will find the Star Wars ep 3 trailers that other people have ripped/converted to DivX/XviD already. Why not start with those instead?
http://www.google.com/search?q=Star+...3+Trailer+DivX