i'm not sure, i just have the beta version running here, but i think MED can save the model as wmp, but not sure (at least you can load wmp into MED).
So if it's a model (.mdl extension), try to open MED, then open your model and click Save As and try to choose .wmp as extention from the file list.
The beta version can important MDL into WED and load it as blocks, so MED doesn't ghave this function anymore, which make it hard for me to check right now.