Some grilles are one piece and need the bumper off to remove.
The bumper is reasonable easy to take off if you take your time and be firm without forcing anything or yanking at it.
1. Take the splash guards off underneth.... 2x clips and 2 screws on each side. There is 2 bolts and a couple of clips holding the bumper to the chassis as well while you underneath.
2. Undo the left and right arches... leaver apart the bumper/arch joint with flat blade screwdriver wrapped in cloth to protect the plastic. Then if you pull back the outer edge of the arch you will see 5mm long recesses. There is push clips at these points. You need flatblade/cloth inserted into hear and push on the edge of the yellow push clip until it releases the inner arch. Theres is 3 of these clipse you need to undo per arch. Then at the top of the arch you will see a phillips self tapping screw which fastens wing to bumper on both sides.
3. Start at one end.. pull the bumper toward you and away from the light...firmly but carefully. Now work your way from one end to the other... pulling on several clamping points along the way.
4. Before you completely pull off the bumper...if you have fog lights on, you might like to push the clip on the connector and slide it off the light on both sides.
That will get the bumper off. Replacement is a bit more tricky although in reverse. Make sure the bumper edge slides into the clamping points below the lights and under the grille. DONT FORCE ANYTHING... firm but careful.
Just under the crash beam you can now see... on the left side... is the outside air temp sensor. This sensor just slides on to a metal prong. It has a plug connector nearby for changing the item. If you battery is disconnected... simply unplug, slide off and replace.
I cant stress enough though... use a cloth to protect the paint at all times