13 years hence, I wanted to add this tidbit of a response to your query which I found super helpful for doing the side markers in my 1993 945T. This is a direct quote from a review of a side marker kit sold at FCP. I was trying to fish wires through without removing the plastic wheel well cover, and found that it was not worth the time (5 mins. fishing wire with no luck). Just remove the wheel well shields, which are secured with five, 10mm (iirc) fasteners (3 metal, 2 plastic). Then you can easily feed the wires through, greatly simplifying this easy job.

"Daniel Stern Lighting has a good tutorial online for the wiring part, but I'll tell you this: Don't bother with trying to fish the wires from the front of the car to the side marker lights (or vice versa). Just remove the plastic wheelwell shields so you can feed the wires exactly where you want them. I taped my wires to the inside (unexposed side) of those plastic shields using a few little strips of duct tape. Very happy with this purchase."