Very easy job, as has been stated. If you have a standard suspension car the OEM Sachs struts are available from many UK suppliers at about £150 a pair for the fronts (much cheaper if purchased on German Ebay-about £100 a pair). if you have M sport suspension they are different spec and only available direct from BMW at an outrageous price in the region of £400 a pair. Much cheaper to buy Bilstein B8's, which are recommended for M sport suspension (again, much cheaper from Ebay Germany-I just purchased a full set of 4 for £460 delivered. If your mileage is 60,000+ you may want to consider a full set but at the very least, as has also been stated, you should renew both on the front.