Since yesterday, I've changed the spark plug on all five of my Kymco scooters. The toughest to do were the Like 200's. The center cover is a pain in the butt to remove because you have to remove the seat/bucket to access all five of the locking tabs to release the cover. Also, the plug is deeply recessed and not easy to start threading in the new plug. I placed a piece of fuel line on the threaded top of the spark plug and that helped get into the recess. It still took me several attempts to get the new plug to start threading properly.
My People 250 was relatively easy. The center cover comes off with two small phillips head screws and a large screw inside the seat bucket. The spark plug was easily accessible through the center cover.
My Grand Vistas were real easy to replace the spark plug. Two phillips head screws and a large screw inside the seat bucket and the center cover came right off. The spark plug is not easy to get to through the center cover, but if you reach up from down below by the kickstand, you can easily get to the plug to replace it. I removed/replaced the plug on my GV's in less than 10 minutes.
I've gotten so good at it, I wish I could do some more ;-).