I found this documentation on using various tools to edit GR2 files. I know very little about 3d modeling, so I don't know how much of this is of any use. I thought I'd post it here so that more knowledgable folks can provide some input as to it's usefullness.
http://gr2decode.altervista.org/docs.html
also this one
http://aoe3.heavengames.com/cgi-bin/...f=14,36458,,10