Since the thermostat in your car has a regular gasket, you can use RTV or not, at your pleasure. If you've had seepage issues in the past, it's almost a given you'd use it. Even if you haven't, it's not going to hurt anything to use it now. If you do use it, only put a thin coat on it, covering both sides evenly. If you put too much on it, you can cause yourself issues. When you tighten down the housing, don't over tighten it. If you start seeing sealant squishing out, you've gone too far. Just bring the bolts down snug and you should be in pretty good shape. While I don't have the spec, I doubt you'd need to torque them beyond 20 lb-ft. You really don't need a torque wrench to tighten these, just try to make them as even as your calibrated hands can and it should be fine. Once the engine has gone through a heating cycle, double check to ensure they are still snug and you should be golden.