The trial version is exactly the same as the paid for one, except it stops working after 30 days. Any projects and events you created will continue to work once you have bought the app.
You can install the whole of FCS on your Mac and it will work perfectly alongside FCP X
You can only access STPs music if you install it and then navigate to it in FCP X.
This article tells you how to install FCS and FCP X.
The initial comments about installing them on separate hard drives or partitions is absolute balderdash.
I and many others have had all the apps installed on a single hard drive for the last year with no problems whatsoever.
The last section of the article describes how to install FCS when you already have FCP X installed.
Message was edited by: Ian R. Brown