Spark plug # 8 is located at the very back of the drivers side bank of plugs. The coil is mounted right on top of it and must be removed before getting to the spark plug.
HOWEVER...leave this job to the professionals. The plugs and coils on these vehicles are challenging to replace at times, being that the plugs can break in the cylinders, threads can strip...etc. A qualified and experienced technician can get you running safely and correctly.
Also - when you have one cylinder failing, the other 7 may be ready for new plugs and coil boots as well.