Basically you remove (cut out) the center piece of the OEM grill then replace it with a high quality plastic/metal mesh or even gutter guard. We used a high quality gutter guard for mine. If you cut and measure right, the grill will look seamless in the OEM frame. It sounds complicated but check out my homeboy's on Car domain:
http://www.cardomain.com/ride/2104497
The picture isn't the best, but you get the idea. My grill is the same, just with the tc badge on the driver's side corner. His has an official TRD badge...