After posting these questions a number of times on various web sites and getting no response, I am beginning to believe that there is not going to be a way to use Kontakt or full GPO with Aria and hence Finale 2009.
Finale does support all VST's now so you should be able to load the KP2 GPO alongside other VSTs (like the bundled ARIA player). I am not a Finale user, so I've been avoiding the topic, but I believe you'll need to copy the KontaktPlayer2.dll file along with some finale-specific instrument definition files over to the FinaleVST folder for everything to show up and play nicely. The procedure should be really similar to the methods to get it working in 2007 and 2008. Read through the stickies above, perhaps?