I tackled the grill installation this weekend. Let me say that if the thought of seeing the front of your Stelvio disassembled gives you cold sweats and/or nightmares then I would suggest you have a professional handle this install or just buy a stick on cover in carbon (I didn't want carbon), or try to get someone to cover it in vinyl. To install the full grill you have to remove the entire front bumper unfortunately as there is no other way to remove and replace it since the screws, tabs, and one nut at the top that hold the grill in place can only be accessed from behind. The top of the bumper and radiator shroud blocks your access from the top.
I am not a professional but I have removed front bumpers before and the modern ones have similar clips that secure it to the vehicle. Also those of you who do not have headlight washers this install will be a bit easier for you as you won't have to deal with the hose that feeds the sprayers on the bumper. You can get enough room to remove the grill without disconnecting the hose to the headlight sprayer on the driver side just be careful to not let the bumper hang by the hose. The actual connector for this hose is buried up behind the headlight and I just didn't want to mess with it since I had enough room to get to the grill with it still attached to the car.
You will need to either remove the front wheel well or loosen it enough to get your hand behind where the front bumper connects to the fender on the bottom. There is a bolt that is hidden here that needs to be removed in order to get the front bumper off. If you wanted to do this the "proper" way you'd probably want the car off the ground with the front wheels removed so that you could have clear access to everything...I didn't do this and the have the scratched up hands/arms to prove it but still got the job done.
1. Open the hood. Locate the 6 large torx bolts (T55) at the top of the bumper and remove them. Easiest part of the job done!
2. Remove the plastic outside fender trim by pulling gently. There are 3 clips that hold it on the front bumper. I would try to stop there as the clips that hold it into the fender are different and very difficult to remove without breaking. You will need to do the same thing on the other side. Had a few plastic clips break. So planning on ordering a few and redoing the fender trim reinstall process at a later date. Its fine and on the car right now but not perfect.
3. You will need to undo a bunch of screws to loosen the plastic wheel liner and to detach the bumper from the liner. They are all T25 torx. I don't have a picture of all of them as some of them are hard to photograph with the wheel on. There is also a pop clip besides the screws. If you've never taken off one of these before, the center must be popped up with a flathead screw driver or pick and then the whole thing can be pried out. To replace you pop in the bottom part first then push the center portion in to lock it.
Its very similar to the one shown below:
4. Once you can move the wheel liner out of the way there is one bolt that is hidden behind where the bumper meets the fender on the bottom portion. I removed this bolt by feel as I couldn't see it. Repeat on the other side. You can see in the one attached picture (Bottom Clips.jpg) the round hole that this screw goes through to hold it to the fender. Be sure to keep this bolt separated as its different from the others.
5. Now move underneath the front bumper and remove the front portion of torx bolts and screws. This will allow the bottom of the bumper to slide off the plastic undertray.
6. Now that everything is unscrewed, go back to the top sections there they meet the fenders. Pull gently to release the clips on both the top and bottom portions. Do this on both sides. Once you do this the bumper will slide off the car. Be careful as there is a wired connection for the parking sensors/radar cruise as well as the hose for the headlight washers (if equipped).
7. On the passenger side slide the grey connector to the left to unlock the connection and disconnect it. Once the connection is disconnected the one connector is attached to the bumper but it will just slide off its post if you gently push it. No need to pull hard here just slide it off. At this point the bumper should be free of the car with the exception of the headlight washer hose (if equipped).
8. The grill is attached to the car with 5 torx screws (T20 if I remember correctly), 1 8MM bolt at the top behind the Alfa badge, and 6 plastic tabs. There is a plastic air dam that is attached to the bottom of the grill using 3 of the torx screws previously mentioned. Once you remove them set the air dam aside. Remove the other 2 screws and the bolt. Push the plastic tabs backwards through the bumper and the grill should come off at this point.
To install the new grill just do everything in reverse. The bumper will take some time to get everything realigned. There are tabs across the entire bottom portion that have to be aligned properly for it to go back on. I found it easiest to snap in the clips where it meets the fender in order to hold it in place to get the bottom portioned aligned.
Take your time, don't get frustrated, use an easy hand on the plastic items, don't let the bumper dangle by the headlight washer hose, and you will be ok. Also keep all the hardware organized so that you know what goes back where.