unless someone hacked up the wiring. it would be the headlight switch. they are known to go bad.
Now if the the "grill system" (think you mean front clip) was replaced THEN it quit working perhaps someone did not connect all of the electric connectors.
So in conclusion
1. if this issue started Immediately after the front end was replaced MOST likely it was not put back together correctly and all the wires need to be looked at that where affected.
2. if the lights WORKED then quit working my money would say the factory headlight switch needs replaced.
http://shop.advanceautoparts.com/web...adlight+switch
ALSO any "toggle" switches would be NON-Factory and i would have no way to know what they do.