1992 Mercedes Benz 300se wiring

A radio was installed and some wires were cut. Now, I am having intermittent use of the windshield wipers; they won't shut off without removing the fuse. The turning signals don't work. The dash readings don't work, and the radio doesn't work. Intermittent use of the heater; will come on sometimes and other times it won't. But, all of the inside lighting works; dash lights, interior lights, sunroof, windows, locks, etc. Which wiring harness do I need to replace or can the wiring harness be repaired? Which one is more cost effective?