Basically if you want to design a site with flash you just do it like you would a movie. Except without a motion loop. You design the buttons and layout. There is a tutorial for creating buttons. There are 3 parts to creating a "mouse over" button. You have to create each of the 3 frames. I haven't used flash in a while but I'm quite sure that the tutorials are very thorough. Check out this site. It has some good tutorials if the ones in Flash don't help.
http://hotwired.lycos.com/webmonkey/...tutorial8.html
Good Luck