Which Files contol widgets in the theme?

[sahdow]

I created a new page template for pages with less content.

I basically copied the default page template renamed it then removed the Left and right bottom sidebars. Everything works , I can select the new or the default template without any issues.

Where I'm stuck is I want to add a new widget, so that I can substitute the sidebar top widget on the new template with an alternate sidebar top widget (not made yet).

This way I could say have a tag cloud and a video on the new template and only have the video on the original sidebartop, depending on the legnth of the page content.

I attempted to do this by editing functions, the style sheet and the page template, but it was a disaster. So I think i'm missing something. Can someone tell me if there are more pages I need to check to accomplish this?