This is just personal opinion, but it's backed by most of the mechanics I spoke with...
On modern BMWs, run what the car comes with from the factory. These BMW engines are rather sensitive to knock, spark temperature, and spark duration that if you use something other than what's spec'ed for OE it may actually decrease the performance of the engine.
As for swapping out spark plugs on the 3 liter, it's a simple enough job. There are two round covers on the engine cover with a small flat notch on it on the passenger side of the engine. Pry those covers off. Remove the torx screws (I think it's a torx 20, don't quote me on it) underneath and remove the oil cap, and you should be able to remove the engine cover. Remove all 6 spark coils, most of them should have 2 screws holding it down AND a bracket on top facing the driver's side of the engine. Pry the bracket up to release the coils and they should pull right out. It may help to disconnect the coils from its individual wiring harness.
You will need to get a ~6" extension for your torque wrench and/or ratchet wrench AND a spark-plug remover. It's basically a long 5/8" socket with a small rubber insert that holds onto the tip of the spark plug. Remove old spark plug. Apply copper based anti-seize to thread of new spark plug, install to 25 Nm or 18 lbs-ft. Reassemble everything in reverse of removal.
