You need to get GFC scape and extract all of the models into your model folder.
Often it doesn't work to compile them to the Valve folder, so make your own minimod folder where you put all stuff needed to make a mod.
Then you add a models folder, and you extract all HL models into that folder.
Now you edit the hammer setup and aim the mod targets at your new minimod, restart hammer, and bang, you got yourself models in hammer!