Interchangable I'm not sure as the 05 grille I believe has 5 bottom retainer clips and the 99-2004 has 4 clips,the header panel may need to be changed as well.
Perhaps others that have done the facelift will chime in with additional info
Yeah, the bumper is different but the Ebay one is already cut to fit. Funny part is, those grills were $500 when the were first put on ebay-now it's down to $280.
Ozhoo trimmed his own if I remember right. It was about 3/4" that he trimmed off. Otherwise, you do have to change the bumper. I have the bumper sitting on the basement floor waiting for my grill/header panel/harness and lights for the mod.
I'll try to find his pictures he took of the grill mod.