think stock is 16 43. I am partial to a DID chain and renthal sprockets.
as far as install tips it should be pretty straight forward. Ull need to take the rear tire off to get the sprocket off of the hub. and the front ull need to remove the cover and the center bolt. I would suggest to remove the front center bole before you take the rear off and to put the bike in first gear. if you start turning the motor over when trying to remove the center bolt either hold the rear break, or put something through the wheel that rests on the swing arm so the wheel cant spin.
Also, at 43k miles what other stuff have you done as far as maintenance if any? Valves still where they should be? im just curious.