OK, I'm new to WordPress,Themes,Widgets,etc., so maybe this is pretty obvious, but when I uploaded and then activated the plug-in and widget I lose all the stuff in my sidebar except the Theme Switcher (which works fine by the way). Any suggestions?

Hi Milo. WordPress gives theme designers the option to load certain functions by default in the sidebar. For example, a calendar and latest posts can be coded into the WordPress theme so that if a user installs the theme and doesn't have any widgets enabled, it doesn't look like crap with an empty sidebar. Then, if you decide to enable a widget, it overrides the sidebar options added by the theme designer so you don't have to dig into the code for the sidebar and delete what was already added. You can then add widgets to replace any of the existing sidebar items you want to keep.

Ah, that explains it. I imagine this was explained in the the instructions for WordPress that I stupidly ignored. Everything works fine now that I activated all the widgets to replace the options that had been preloaded and then "widget-ized". Thanks for the explanation.