If it's a sealed chain it's probably OK to use it with the new sprockets with so few miles on it. Obviously you won't need quite as much chain because of the three teeth smaller rear and one tooth larger front, but whether or not you need to take off a link depends on where in the swing arm slots the axle is now. You'll be able to tell when you change the sprockets, and if you need to take out a link you can grind off a rivet head and drive out that rivet with a punch.
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