2003 BMW X5 small electrical fire

My car has had a minor electrical fire where the cd changer and sat nav unit is located (rear boot nearside). Alot of the wires are burned but it seems limited to the entertainment system (cd changer tv sat nav etc) as this does not work. Although there are wires there for the rear lights etc
i have located a wiring harness from a donor car, my question is is it possible to mesh the two wiring looms together? Eg just cut past where my wires are burned and replace with good wiring from the donor car or does the loom have to be installed without any breaks
thanks