I am about to install my HID kit on the c-coupe.

I know that after it is installed, theon-board computer will register it as failed lamp as there is not the resistance of the filament when the computer checks

Are dealers usually willing to reprogram my c-coupe for the xenon-light setting to make it acknowledge the presence of my xenon-light ?

I doubt it, because some outdated and stupid DOT and state laws says that retrofitting headlights is illegal.