No experience wBMW strut replacement, but if you decide to diy’er this job, I’d recommend you buy the parts from the BMW dealership, ask for the oem parts. If they ask about our car’s configuration, just give them the vin number. They can figure out everything they need to know from that. If they can’t, go to a different dealership.
You might could get away with aftermarket parts, but then again you might not. Not worth the risk imo. Not sure how your suspension is configured, but on my Corolla both front and rear are a shock absorber gadget positioned inside a coil spring. The difference front to rear – besides the spring and shut physical response constants – is the front one is part of the steering system, has to rotate when you turn the steering wheel, so is a little differently configured the way it interfaces to the rest of the car than the rear one. But everything is still a shock inside a spring basically. A strut in other words. The coil spring component rarely goes bad, especially in a newer car like yours. But it is easier to replace the whole strut as a unit rather than just the shock. So you got the choice of either buying a whole new strut, new coil and new shock. Or just the shock gadget, using the existing spring.
I think it is better to just buy the shock gadget, and keep the existing springs. There’s no problem with the existing springs, so why take a chance of introducing a new problem? At that point you have a challenge of how to install the new shock in the old spring. Suggest you don’t try to do that yourself. It can be a dangerous job without the required experience and shop equipment. Take your old strut to a shop and pay them to do it. The parts place where I buy the shock gadget, they’ll insert it into my old strut for me for a small fee.
Secure the shop procedure and read it carefully before beginning. The strut is a structural element. It holds the entire weight of the body of the car. When you remove it, the body will want to drop on top of the axles, which could damage things you don’t want damaged. So you got to do stuff to present that from happening. What that stuff is exactly is in the shop procedure.
If you’ve done anything moderately complicated before, like replaced a timing belt, or replaced a fwd half-shaft, you should be able to do it yourself. I"d say that is a certainty if you owned a Corolla. A BMW, being a performance car, may offer up some additional challenges. So do the necessary research to know the entirety of what you are letting yourself in for before beginning. Best of luck.
Oh, I’ll add that when the job is done you’ll wonder why you waited so long. It will feel like a new car again.