You will have to remove the 4 screws at the bottom, and then pull the inside panel free for access to the mechanism. If the door is stuck closed, you can manipulate the inside panel loose from the door at the top enough to gain access to work the linkage by hand. It is not fun, but can be done without ruining anything. You may have to get some new 'christmas tree' plastic fasteners if the old ones are too distorted to work.
tom