Where is the cigarette lighter supposed to be on a 2003 Buick Lesabre

YES

cigarette lighter has ONE wire, attached to center contact on the back end, and grounds via the case, or a wire attached to the case and the other end to the support structure of the dashboard.

I imagine it ought to be located in the ashtray on one side. That is where it is on my GMC pickup.

Sounds like you shorted out the cig lighter which can also power other circuits. Have you checked the cig lighter fuse ?

I think that fuse is under the hood in the higher amp fuse box,it sould be marked & the fuse id will be on the lid

It is located in the fuse box inside car. However, many GM vehicles share fuses with multiple devices. The radio fuse may also operate the cigarette lighter, and so on. My 1991 LeSabre shared fuses. Check fuses to see if any are blown.

if not listed specifically, the fuse should be listed as accessory in the owner's manual

i had the same problem with my 2003...it was # 32 fuse under the hood labeled front auxillary

It is usually a yellow wire. You may also use the wire from the cigarette lighter or any wire that is a constant 12 volts.

First of all, you had a short in the electric system that included your cigarette lighter. When you saw the spark, you saw the result of a short. What you are experiencing now is a bad ground in the system.

This is what we refer to as stray voltage, which is why your lights are staying on. This is not aa fuse problem. If you haven't unplugged your cigarette lighter, do so. You are going to need the services of an automotive electrian to solve this problem. The reason your cigarette lighter may have been unplugged is that someone else knew of the existing problem.
Bill