I had the same problem - intermittent leak inside the trunk. The rubber gasket around the taillight had rotted away. I just got a cheap generic rubber gasket at autozone and replaced the rotted one with it.

I don't remember exactly what I did to remove it, but there are some nuts on long screws that hold the taillight on. I do remember it wasn't very difficult to remove.

Steven

Steven '98.5 SVT DMD, K&N, Magnaflow res, Falcon floormats, electrochomatic rearview mirror and other little goodies