This can't be that hard to repair, just carefully cut the burned section apart, don't cut the wire out until you get to good wiring, then just splice in a new one. Just note wire sizes and colors. I've done it a number of times. (Once on a Porsche took 3 days of laying on my back under the dash, about 30 wires if I remember correctly). There's a wiring diagram for a B600 on Amazon right now.
Pretty simple stuff, no computer or fragile sensors to deal with.