Replacing Door Lock Cylinder... help PLEASE!

I am the proud, yet frustrated, owner of a yet-to-be-working '89 Pontiac Bonneville SSE.

When I removed my door lock cylinder, I managed to disconnect everything from the cylinder except for a single irksome cable. It is black and seems to lead to a lightbulb (?); however, the light-bulb is connected almost like a fuse. The black wire leads to the tip of it while the bulb is connected on the opposite side via another cable but the two parts connect together: I don't understand the use of the black cable.

Anyways, the wire connects at the very front part of the cylinder near the outside part of the cylinder and I assume its use would either be to cancel the car alarm, to light up the instrument panel when used, or for the power-locking feature.

The problem is I can't find a way to remove the lock cylinder because the wire is connected in such a way the only viable way I see to separate them is by cutting the black cable and I don't want to do that without understanding what it is and if I should do it.

The new lock cylinder set I got does not have this black cable connection and none I could see at the store had them either.

Any help would be greatly appreciated,

Thanks,
Andy.