It shouldn't fail as long as you have a spark plug socket with a rubber retainer in it. also it depends on the state of the cam cover gasket around the spark plug holes. A pattern one can get in the way and its a nightmare getting the socket down in there.
Also when putting the new plug in as VR6 said with an extension and socket by hand, reverse turn it first and you will feel it clicking as it spins on the threads. when it clicks turn it clockwise and it should seat and do up without knackering the thread.