51217112443 Here is the part number. Go to Realoem. Com and put in the number and you can see where it goes(there is an excellent exploded view) As to installing it, there is a definite correct procedure and it might be best left to an experienced BMW technician as trying to DIY is possibly going to be very costly. If however you intend on trying to replace it yourself, the best advice is to obtain a comprehensive repair manual, I recommend Robert Bentley publications, they are the best. Amazon. Com will be a source. If there are questions along the way, please come back and ask them.