Yes, is already updated
No, is not hard but its a long process. And I think some models can't be ported right now.
Probles to port them:
1)(General) The big problem right now is the particles. I try to make it from 0 and didn't work. I'm working around this.
2)(General) The billboarded bones, as you know, are used by most of the models of warcraft and right now, the .m3 plugin can't suport it.
3)(Only Buildings) The birth animation of buildings (Human and Orc)
4)(General) GeosetAnim to hide geosets in .m3 models is unknown right now.
5)(General) Animated Textures, I don't really know how this work in .m3, also the plugin don't work with this.
6) GlobalSequences is really useful and alot of war 3 models uses this, and .m3 can't work with this, or the plugin don't support this feature at the moment.
But apart for this, the warcraft models looks really good with a normal and specular map:
So, the effort is worthwhile.