To upgrade from version 1.x to the lateset version, follow this guide.
Make sure you update all CSS and JS files that are related to AdminLTE. Otherwise, the layout will not function properly. Most important files are AdminLTE.css, skins CSS files, and app.js.
There are major changes to the HTML markup and style to these pages. The best way is to copy the page's code and customize it.
And you should be set to go!
Mailbox got an upgrade to include three different views. The views are inbox, read mail, and compose new email. To use these views, you should use the provided HTML files in the pages/mailbox folder.
Note: the old mailbox layout has been deprecated in favor of the new one and will be removed by the next release.