every part you want to split has to be in a separate mdl7 group for my tool. for example if you feed it landscape.mdl which has 5 huts on a hilly terrain in it and every hut is in a separate group it spits out:

landscape_0001.mdl // contains the hilly terrain
landscape_0002.mdl // hut 1
landscape_0003.mdl // hut 2
landscape_0004.mdl // hut 3
landscape_0005.mdl // hut 4
landscape_0006.mdl // hut 5
landscape.wmp // contains all models at their correct position



i think med would load the textures for .x files automatically. isn't there a .x exporter for cinema4d? the new med can also import groups from .x files (and probably other formats too) so depending on your exporter and the format you use you could get a model with groups directly out of cinema4d.