spark plugs

Like often: It depends! It depends on how exactly "they look bad" looks. If the spark plugs are just worn, but look evenly in color and state, just change them. If you have different colors and the engine runs bad after changing the spark plugs, i would recommend testing the air intake system for leaks by spraying brake cleaner. Furthermore, valve clearance needs to be checked. If you have done that already not too long ago, everything is fine. If you do not know, when this was last checked, do it. If the valve clearance is fine and you cannot find air leaks in the air intake system, you could sync the throttle bodies. It does not make much sense, it the preequisites are not met.
Correct oil level is in the midlle of the looking glass on the roght side of the engine. The bike has to be on the center stand and the engine has to be stopped for more than 5 minutes, to give the oil enough time to return to the oil reservoir in the oil pan.
An oil level up to the upper mark of the looking glass circle is still ok, but most Kays start using more oil if the level is that high. Lowest allowed level is the lower circle in the glass....so do yourself a favour and keep it close to the bulls eye