How to remove broken car air-vent cupholder?

When we bought our '90 Nissan Maxima 13 years ago, it had a cupholder attached to the center dash air vent. It worked fine for many years. But now for some reason it hangs down too low, holding the cup at too much of an angle. It's useless, and I'd like to replace it or at least get rid of it. But I don't see how to remove it without damaging the vent. It has two arms which extend back into the vent. Any suggestions on how to remove it without damaging the dash, and without ending up with the rear ends of those two arms rattling around inside the vent?