The deployed process is in the database. While deploying (with the 3.0.8 GPD) you have the option of saving an archive file somewhere locally on your hard drive. You can then use this file to do the deployment with the deploypar ant task if you like.
Undeploying can only be done by deleting the processdefinitions from the database. But be warned because this delete will also delete all your started processinstances (which are dependent on a particular deployed process definition).