Hi,
I've updated the Wiki, thanks.. the skin/plugin installer is included in the aMSN installer .dmg file when you download aMSN, use it from there...
about the music and growl plugins, you should download/install them manually since they don't come by default with amsn (apart from the mac package).
About your last question, please read here :
http://www.amsn-project.net/forums/viewtopic.php?t=6702 as I've explained what I'm currently working on with regards to your issue... don't forget this is the SVN version, so it's in constant development and things might be broken but we'll fix it soon.
thanks.