First off, welcome to MLF, we are glad you're here! The 17 is a single cylinder and your spark plug should be located on the front right side of your engine. It should be accessable from the right side of your mower with the hood lifted.
Mr. Five Points is right on the location. It's almost totally opposite of the oil filter.
Here is something you might like, the owners manual for your machine. It's in .pdf format so you can either download or reference online.
How are you as far as oil change? Have that taken care of or is it something that you feel you might need some instruction on? If so, drop back by and we'll walk you through that task. Pretty easy and it's a lifesaver for the engine.