It would have taken less than half the time you spent on google, to go out and change the plugs..
You have to remove the console, gas tank and airbox to change the plugs.
Open the seat
remove the console and both side panels
remove the spar panels. (#1)
remove the support tube (#6)
remove the screws holding the knee pads to the chassis (#10)
unplug the fuel pump wires, and fuel line (press the button on the quick connect at the top of the tank)
Slide the fuel tank to the rear, or take it off all together.
unplug the air temp sensor
remove the screws holding the air box to the chassis (#22, 23)
loosen the clamps holding the airbox to the throttle bodies
Slide the airbox out of the way.
unplug the harness from the coils
remove the screws holding the coil (#25)
remove the coils.
Both the spark plugs, and coil retaining bolts get tightened to 96 in/lb
Here is a pic of the split airbox kit, that allows you to change plugs by only removing the console. It was factory installed on newer sleds.
Fouling a plug on the Z1 engine isn't very common, and almost always caused by starting the sled, and moving it, reving the throttle, and/ shutting it off before letting it warm up.
Any time you start that sled, it needs to run long enough to warm up. The worst thing you can do is start it, move it, and shut it off.