Change Content Depending on Page Selected?

After I get done creating the widgets and all the other elements of a theme, is it possible to have different content or images displayed in the widgets (i.e. text widget) based on what page is being displayed using php code to find out what page is being displayed?

You dont create widgets, but you style widget areas. Displaying content differently on different pages - as explained in your other post, use Dynamic Widgets or a similar plugin.