Just changed my harness today due to complete wiring failure (the wires had corroded so much they fell out of the connector when i was taking it off). It should take you up to 2 hours:
(My car's a late 2004 C6 3.0 TDI Quattro, Saloon, regular suspension)
I used this handy video for reference ->
* Phillips screwdriver for the storage belt buckles (no idea how they are called actually... the four shiny things on the floor of the trunk, two on each side) + 10mm socket for removing plastic molding in trunk
* Torx screwdriver/bits needed for removing the wheel well liner
* Soldering iron for the wires + some heat shrink/electrical insulation tape
* A new harness
1. Remove (partially, pull to the side as per the video) the trunk carpeting on the side you're going to be doing (i found it easier to get it done before the i jacked the car up). Once you pull it to the side you'll be able to see where the harness goes in the car and connects to the main loom. Be careful with the plastic clips holding the plastic molding/carpeting... i broke two and i was super careful
2. Jack the car up and put on axle stand if possible, remove wheel, wheel well liner (you could power wash it first so you don't get dirty and it will also be easier to find all the torx screws holding it in place)
3. Unclip all connectors (EPB motor and Wheel speed sensor in my case), remove two plastic clips securing the harness to the suspension arm (by pulling/sliding them straight towards the brake caliper) and maneuver the harness from behind the brake line (be extra careful there) so it's ready to be pulled out.
4. Cut the wires on the inside (in my case - epb cables + speed sensor wires) - leave as much as possible of the old harness so you have room for error when soldering/cutting.
5. Pull the old harness on the outside taking off the rubber weather seal as well.
6. Maneuver the new harness in place (outside) and run the cables inside making sure that the weather seal fits snug. Solder the wires on the inside and insulate them well before attaching the connectors on the outside. Attach all retaining clips, refit well liner, trunk carpets, plastic moulding, wheel back on... and you should be done
cycle the EPB on and off a few times to make sure everything's good.
It might be a good idea to disconnect the battery but i personally chose not to. If you cut wires one at time and you take the time to ensure no wires touch each other/any grounding points i believe there should be no need to disconnect the battery for this operation. Just remember to observe the cable colors, solder first and attach the connectors second.
Hope this helps. Dealership here wanted 75 Euro (100-ish US$) for the harness and 70 for the fitting...