Removing the trunk cylinder without the key may be a problem.
You have to remove the 4 8mm nuts and the one 10mm in the middle holding the black bar holding the cylinder.

What may be a bit harder is that the central locking linkage is attached with a small screw to the plastic part of the cylinder, this may hard to reach.
It may be necessary to drill a hole to access this screw if you can't turn the key.

May be an other dealer is more helpful with a replacement key.

Rob