The valve cover on my 2014 X1 cracked also. As you probably know this seems to be typical for these plastic valve covers. Mine started leaking around 100,000 miles, but it might have been before that. Oil was dripping onto the exhaust manifold and causing quite a mess and smell.
I just now decided it was time to change it at around 138,000 miles. I was putting up with the smoke and smell until I decided how I was going to fix it. Thanks to YouTube doing it myself seemed plausible. There are some great videos showing how to do it. This is the one I used:
I also changed out the spark plugs while I was at it. Total cost for parts was around $200 through Amazon. Good luck!