I say see if the dealer will do a goodwill repair. and or contact MB USA and discuss with your local regional rep the possibility of repairs.
It can't hurt to ask.
Otherwise see how much the part is through this site, partsshop, call phil, and see how mucht he independent will charge to repair it.
If the car is this well maintained and needs a harness, then I would think it should be fine once it is done.
Try doing another search on goodwill repairs or wiring harness etc. etc.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.