2006 Ford Taurus 6cylinder 4dr.

My sister's 2006 Ford Taurus has a wiring harness problem. After the mechanic she brought her car to tried to match up a used wiring harness at the auto salvage yard, he came back with the wrong one for her car. The mechanic put back the original harness and did'nt leave her with any options what she hould do. Does the Ford manufactures still make replacement wiring harnesses for that year or does my sister have to try other auto salvage yards to find another used replacement wiring harness for her car. The car does not stay running very long and stalls out after the engine light comes on and leave her stranded sometinmes in the middle of the street. Then she needs a jumpstart to get going again for a little while untill it happens again. What should she do?