2001 Lincoln LS wiring harness

We have a 2001 lincoln ls, v6, with 73000 miles. We had repair done previously but are just barely over our mileages (By 1000 miles) for the repair to still be under warranty. The wiring harness was repaired/replaced, and it isn't working again. I don't even know exactly what it does. But our brake lights don't work, I do know that. Is this a simple thing to fix on our own if we get a manual? I removed and replaced the alternator in my 95 GT mustang a couple of years ago, with the help of the chilton repair manual (just so you know my level of repair knowledge and capabilities to this point) What is your advise!