wat do u want to do with him? edit the model? if u wanna edit the MODEL in milkshape3d then open ms3d then go to file then go to import then go to Half-life SMD and chose the smd u wish to modify... if u want to edit the SKIN then open ssvegetabody.bmp or ssvegetahead.bmp in ur paint program and edit...
*edit* by paint program i mean ex. paint shop pro or adobe photo shop... i do not advise u use ms paint cuz its pretty bad...