1) Xith3d has a View class, you can set where it is in the scene and what it looks at, so you don't have to calculate the object transforms manually (if this was the case there is not much point to a scenegraph). Checkout the Getting Started Guide on xith.org. Example of the View being set:
new Vector3f(0, 0, 2f),
new Vector3f( 0, 0, 0),
new Vector3f( 0, 1, 0));
2) The collision code is currently unsupported as the original author is no longer activly maintaining it. I personally don't use it, and instead use Odejava for my physics and collision. Odejava is more heavyweight than the Xith3D collision (a whole library with native binaries in itself) so it's not an exact replacement, I'd only recommend it if you utalised many ODE features.