Related question - is there a seal between the thermostat housing and the engine block? Or is the seal done just by the O-ring that comes with the thermostat?

As far as draining the coolant to swap the thermostat, do you have to do it with the drain nozzle on the left side of the block under the exhaust manifold or would it be easier to drain some by disconnecting the bottom radiator hose?

Thanks.