Does Gmax import Collada files very well? If not, is there a plugin/other free program that will work?

I doubt you will find something. but i never heard of a collada file type before.

Collada is a type of "standardized" file format by Sony, in an attempt to standardize 3d files so that you wont need a new plugin for every format used by a 3d modeling program.

I am wondering this because Google's sketchup (free version) currently supports Collada as a file for exporting/saving, it can be used in Blender, for example.

Finding a plugin that would do this is just about as easy as searching for ways to open compiled maps with sapien. (i.e. Decompiling/Decompiler)

Trust me when I say I searched, ive searched.

That's sad, because if someone would make a plugin for it for either sketchup or gmax, Map making would probably become 10x easier in terms of modeling.