Flash layout transitioning questions

hey! i recently posted about how to create smooth transitions for my flash layout. i was able to get a good response and found out how. i used this tutorial from kirupa:

http://www.kirupa.com/developer/mx2004/transitions.htm

it works fine, but i was wondering if the buttons have to be actual button symbols or if they can just be rectangles, because if i make them button symbols they cant be complex buttons. and secondly, i tried to put the preloader script in the external swfs like the end of this tutorial says but i had problems with it, so i was wondering if i can just use any preloader script and place it at the start of the external swf and it will work fine? thanks in advanced.