Really depends on what your ahole of an ex did. (BTW did you file a police report for criminal damaging?) If he cut part of the wire harness then that will have to be replaced. He may have removed modules or relays, which can be replaced without too much trouble. Obviously a shop will have to look at it to see exactly what it needs. As far as wiring goes, there are a few major wire harnesses; the battery harness, engine harness, instrument cluster, and body harness. The body harness is the big one it can run from front bumper to back. The engine and instrument cluster may be the one that comprises the anti theft the most, although that can also involve the body harness as well. In the future, get a tow truck to tow you, that way there's minimal chance of additional damage, being pulled behind another vehicle by tow straps or a tow bar is risky and it forces your transmission to operate without the benefit of a running engine and operating oil cooler.