Q: Timing belt or chain how much to replace. Buying used not sure if it done

The RX350 has a timing chain which does not need replacement. While the timing chain does not have a service interval per se, timing chain engines such as this have longer term maintenance requirements in that the timing chain tensioner can become weak, and timing chain guides can eventually wear through - causing major engine damage. With your advancing mileage, if you hear irregular metallic noises from your engine, these components may need service. Since you are buying this vehicle with quite a few miles on it, I would recommend having YourMechanic.com perform a Pre-Purchase Car Inspection on this vehicle, which provides an accurate assessment of damage, and estimate the cost of repairs. YourMechanic.com can dispatch a mobile, professional mechanic to your location for diagnosis and repairs. Contact YourMechanic.com to request this inspection and to schedule an appointment.