Is this still open for visitors? And does anyone have info for a guide to explain the reliefs?

As of September 2003 it was closed with no re-opening date posted. The link <-- includes a "tour" with some explanation of the reliefs.

One more thread from a couple of weeks ago; still closed.

The latest word is that it will not be opening until spring of 2005. There has been many of problems. The largest is due to the Superintendent of Archeaology of Rome. He had declared the supporting structure would impose too much damage to the ancient ruins underneath the complex. Because of this, the city had to re-plan with the American Arhcitect, who designed the structure, Richard Meier. This caused delays and a 20% increase in price to the city.