Surly someone on this forum knows how to gain access to the plugs on a 550! I would think this would be the forum to be part of to find out something that simple.
George
First of all, George, welcome to the forum.
As these 550's have only recently came out, a slower response time should be expected on these types of failure/problem questions.
I assume you purchased this gator new from a John Deere dealer?
#1 - contact your dealer, this type of situation should be alleveated under warranty.
#2 - ALL new John Deere equipment includes an operator's manual. If you didn't receive one, again, call your dealer. Part number is OMM164562 - English
#3 - Read your operator's manual. Page 44...the plugs are located under the back bench seat. You'll need to remove the center plate (the piece that looks like a toolbox tray). Spark plug gap spec is .762mm (.030 in.)