The cluster will have to come out. The rest is basically freeing up the old cable and removing it. I haven't done this on a Benz yet, but on other makes, we used to tape the new cable to the end of the old one inside the car and pull it thru that way. Not sure if this will work with the 300E. Maybe Benzmac or Steve B. can help here..
2000 Dodge Grand Caravan SE