If you want the best fix for the least money, just replace the plug resistor itself. The factory originals can be purchased aftermarket and it leaves you with everything top quality. A set of wires will require a lot more work, a lot more money, will be hard to run as originally laid out, and unless you know how to buy right will leave you with a POS.
If you just like spending money replace all of the ends. If you just wish to fix the car (since you have been able to locate the bad one) only replace the one in question.
The job is very, very easy if you follow a couple easy tips. The main problem you will encounter is that the end will not properly unscrew from the wire. The plug wire has a male metal electrical connector made to the end of the wire. It is a separate part with a MB part number but you do not want to have to replace it (just a lot more work). The problem is that like a lot of screwed together things it takes a certain effort to break loose. This effort will usually rip the wire from the metal end (which is screwed to the female end of the plug connector.
To solve this problem, take a knife and slice the rubber boot that is part of the old plug connector. Remove the rubber and there will be about an inch and a half of white ceramic before the metal heat shield. Take a pair of strong pliers and with a rag covering the ceramic sqeeze the rag till the ceramic shatters. Pick away the pieces. Watch out they are as sharp as glass. You will now have the metal connector exposed and it is easily turned at this point so that no stress is placed on the wire to connector union.
Soap up or lube with silicone the old wire and install into the new connector and tighten till seated (lightly - it will be apparent).
Bosch Master, ASE Master, L1
33 years MB technician