Both of mine showed signs of melting after 16 years just using the stock 55/65 bulbs. One eventually failed. The stock connectors are already under-built, and are certainly not up to the task of taking higher watt bulbs.
The replacement connectors from NAPA and Autozone are actually superior to the stock ones. The contacts are more beefy, and the wires are fatter.
Also, it looks like MB will only sell you the entire harness, so that must be big bucks. I'd stick with the aftermarket repair.
Is the rest of the circuit up to the task? Probably for 55/100, but I really do not know. You may need to 'hardwire' the lights with fatter cables, and switch the circuit with a relay. This would also ensure less voltage drop for full 'brightness'.
Best of luck.
1986 300E 5-Speed 240k mi.