parking sensors broke

Some smarty pants pushed in one of my rear sensors. A stupid friend of mine drilled the center of the sesor so that he could put something in there to hold it while the glue set. Then patched the whole. Now, none of the sensors work. OK, honestly it was NOT me who did it (I swear). What will I need to do, replace the patched sensor?

Thanks!

[Gilly]

Yeah, you'll probably need to remove the bumper to replace it, too. You can't drill a hole into the sensor (duh).
No idea why they all quit working, may be a safety feature of some sort.
Gilly