The quickest way that I found (in my mis-spent youth) to break into an 113 trunk causing the least damage was to take an ice pick and punch a hole through the rubber gasket and the sheet metal of the rear pannel above the lock housing just slightly to the right of the trunk relsese button.
With a piece of stiff (coat hanger) wire feel around untill you find the trunk release lever press (forward) on the lever and the trunk will pop open. Once the trunk is open, you will be able to take out the screws from the latch plate and the lock assembly and find the problem.
If you punch the hole close as you can to the chrome housing, a new rubber seal will cover up the hole.
I'm riding 50Km. on my Unicycle 18 May, 2008 in the Tour de Cure.
http://main.diabetes.org/goto/al.lieffringPlease help if you can by sponsoring my ride.
Al Lieffring