I had FCP open and selected some option (don't remember which one) from, I believe the View menu, and my whole computer screen went black.

Now, whenever I open FCP, I get two windows, Browser & Viewer Slug, but no menu bar at the top. If I click anywhere on either window, my computer screen goes completely black. Clicking on my mouse just gets me back to my Desktop and the same two FCP windows.

Does anyone know how I can get out of this black hole?

Try to trash your Prefs

That always seems to fix those kind of problems.

Pref is located at

Mac HD / Users / your user name / Library / Preferences> Find com.apple.FinalCutPro.plist

First try Command F12. You may have set your video playback device to Digital Cinema Desktop, meaning your video plays on your monitor full screen. It is also located at View> External Video Device. Command F12 is the shortcut to enable/disable the video playback.