Are you sure you know how to check?
If the wiring harness has been replaced, then you're in luck.
If it's the original harness, I am 100% sure that the insulation has turned white-ish in color and is either flaking off, or has completely turned to powder, exposing the copper wires.
I took a utility knife and carefully slit open the black fabric covering the wiring harness on the firewall behind the engine. The insulation on the wires looked like new, it was intact, and the insulation on the wires had many different colors like it should. I visited the dealer and had a vehicle master inquiry printed out, and it showed me that it was, in fact, replaced as a "good-will" warranty in 2001 at 107,000 miles by the previous owner.
If you're unsure of checking it yourself, take it to a good Mercedes mechanic or the dealer and have it checked out. You may try and plead your case and getting it replaced as a good-will warranty. They might cover the cost of the harness, and you'll have to pay for the labor.
FWIW, the harness will run you about $550, and many techs have posted that it'll take 2.5-3.0 hours to replace.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".