URL problem: www.sitename.com/blog and www.sitename.com/learn using same WP installation

Not sure I exactly understand your problem, but it sounds like what you want to do could easily be accomplished using Custom post types: http://codex.wordpress.org/Post_Types#Custom_Types

This would basically allow you to have an entire segment just for ‘learn’ completely separated from your general posts/blog – you could even give ‘learn’ it’s own styling by using if ( 'learn' == get_post_type() )