Newbie at Youtube Animation/MacBook user... how?

[Chi2]

I have a MacBook laptop and I'm a new user to youtube.
I was wondering if there is some way that I may record quick clips from movies using my MacBook.
I know I can play dvds on this.
And also, once when I have "downloaded" my clip, is there anyway to replace the sound with my own music?
Thanks for your time and help!
(I'm also new here, so I'm trying to find my way around still).

 

[Chi2]

Also, on a more general note:
how can I find this thread again, and/or subscribe to it?