As a result of questions regarding Garritan Personal Orchestra and GarageBand- I found a link on how to combine the two.
http://www.garritan.com/tutorial/UsingGPOinGarageBand2.htm
If you can squeak the $199 and want to integrate GPO into your recording easily – do this – you should get a tool designed for it – like Apple’s Logic Express, or the premium version Logic Studio ($499).