That was just a photo I had that showed those plugs but also showed the pedal. Checking those plugs wont tell you much except that the reservoirs are full.
But I would check the oil closely, radiator, etc.
Also while it's running watch for smoke/blowby coming from the tube by the left side of the radiator. Blowby indicates worn engine.
To get at the spark plugs you will swing the battery tray out like in the picture below.
This is a diesel but your gasser is the same
except smaller battery.