Congrats on the purchase!
Usually with every used machine that I purchase, I always go through it and do a tune-up. If it were mine, I'd most likely buy a JD tune up/maintenance kit that includes oil, oil filter, spark plug, air filter and fuel filter. This way it'll all be ready for the mowing season.
Maybe clean it all up nice and good too if it's not already, totally your preference. Checking the condition of the belts and having the blades sharpened (if they need it) might not be a bad idea either.
Most of all, just enjoy your new purchase.
