Outside diameter of the 17" is pretty much the same if you are using standard BMW recommended tyre sizes on 19" or 20" rims. (higher profile on the 17")

I am not sure about pre facelift, but facelift requires special oil (fluid) for transfer case. I did mine and bought fluid from bmw dealer for about $60 AUS per litre. Luckily only requires .7 lt. If you have a "transfer case oil abrasion error" changing fluid alone won't fix it, you need to reset ...