2003 Hummer H2 How to remove/replace the rear tail light ju

Hello,
I've narrowed my troubleshooting of the driver's rear taillights and license plate lights down to a problem in the rear tail light junction block. This part is common to later models of GM Trucks (at least). It looks easy enough to remove the unit from the vehicle, however I've tried getting it out by prying it forward with no success. How is this removed from the vehicle? I dont' want to break the current one, but need to k now how to remove it before I buy a replacement.