Keyboard shortcut to display music library in iTunes
Just use Tab.

If you start with the focus on the playlist and hit Tab, the focus will go to the sidebar. You can start typing Mus and the Music library will display in the main panel. Hit Tab again. The focus will jump to the search bar. Start typing the song you're looking for. Hit tab again and you're back in the main window where you started.

You can use OptionCommand + f to jump to the search box at any time regardless of where the focus is.

It sounds like you'd benefit from an app launcher with built-in iTunes launch/search navigation. Quicksilver and LaunchBar are both good choices.