So I wanted to show you what I replaced on the wife's e91. I post this info since the 1 series and the 3 series run the same N52 motor. The pics below show what I had to replace.
This is the failed bolt...
This is the replaced bolt. You have to remove the all of the parts covering the engine cover so it can be removed, the airbox and you have to slide the intake out of the way so you can get to the bolt to torque it. I have about 3 hours invested in this repair. One item of note. Make sure you clean out the bolt hole of any oil. If you don't, you'll never get to the 21ft/lb of torque plus 90d of angle torque. I snapped a new bolt in 2 because I didn't clean it out.
It's a fairly easy job, just take your time.