A used Marlin .17HMR for $200 isn't a great price. If it was the stainless steel model with fluted barrel it would be a descent price. But it sounds like the plain blued model. If so you can get one at Walmart for around $170-180. As for coyote I'd use the Gamepoint ammo or TNT ammo and keep it between 50-75 yards. That should do the trick!! Good luck you'll love that gun!!