Ok, assuming the key assembly is the same as my 92 w123, you'll find the lock cylinder/assembly has a T shaped connector that fits into the latch assembly. If you shear off the pot metal T connector the lock cylinder will turn but not affect the latch. The latch then has I think a electrical connector(s) that indicate if the assembly has been opened/closed thus telling the convinence relay to close the sun roof, or the alarm system the state of the lock/unlock state.

The maintenance manual has instructions for removing the door handle and lock cylinder.