Welcome, but I strongly advise doing the job properly & removing bumper, just so you know its fitted well, its only few hours work tbh, you could try loosening the bumper at top & one side & seeing if can get in behind with your hands but I just fear some cracking on other side from flexing it to get in there, I'd take it of & replace that way, I actually also screwed mine to the bumper & glued it so it didnt move, rattle or come loose etc, so benefits to full removal.