I  am looking for a new media player and I was wondering if someone could tell me if Amarok has these features:

1) show a list of the last 100 songs played
2) Does it have a media library? if not, how do I show my whole collection of music(other than a playlist)?

1) not really... If you use Dynamic Playlists it will show a list of the latest played songs ( of configurable length )
2) yes, definitely! Amarok has a very advanced medial library ( called the collection ), and we actually strongly recommend against adding everything to the playlist at once. Based on your collection, you can build the very powerful aforementioned Dynamic Playlists. ( see http://amarok.kde.org/wiki/Dynamic_Playlist_Walkthrough )