Hi
Java3D is completely different from Java2D and Java3D 1.6.0 (and 1.7) cannot be "installed", it's just in your classpath, it mustn't be put into the JRE, it mustn't rely on the extension mechanism...
Why not looking at some simple examples (compatible with Java3D 1.6.0, but not with Java3D 1.7.0):
http://java3d.org/samples.html