Not to be confused with an expert of anything, here's my .02.
As of PS7, a scripting plug-in has to be downloaded from Adobe. I don't know about CS. All action functionality is built into Photoshop.
Since Java and VBA are programming languages, having programming experience is almost a must in order to craft scripts using them. Although actions have considerably less functionality, they are very powerful and can be recorded by those who have never dreamt about programming a computer.
A very good PS scripting resource is the Scripting forum at www.adobe.com.