I'm a massive fan of Opera, but I can't figure how to flip the GUI back to where the main titlebar is hidden again. Any ideas?
Back to its original look:
Under Appearance - Skins, choose "Opera Standard".
Unselect "File|Show Menu Bar". If you don't want to see the tab preview, drag and drop the tab line up:
+--------+ +--------+
| | | |
| | | |
| | | |
+ +-----------------
drag this line up ----^
(I hope I'm understanding your question correctly.) Press Shift-F12, then change the appropriate checkboxes under the "Toolbars" tab to suit your needs: