Here is an idea that may work and not cost too much. If you can get the trunk a little open then why not slide a hacksaw blade in there and saw off the latch part(or maybe even get to it with a wrench, I think 3 screws hold it on), then you could open the trunk and replace the defective deadbolt and all you would have to to is get a new latch, sounds better than drilling a hole in the body(yikes). What do you think?
1985 190E 2.3-16
1984 280GE Cabrio
1957 220S(running one day, I hope!)