After replacing my waterpump belt and seeing how they would have to get to the pump area to replace the gasket, i would say even if that was american dollars that would be almost reasonable, to me at least...I don't think I am confident enough to remove all that stuff that has to come off.
As to the CSS...I can't remember, I was just at my dealer a few weeks ago where a Deville owner had to have his replaced, i forgot what the service guy told him.
EDIT: According to
www.rockauto.com the AC Delco part cost for one Crankshaft Position Sensor is ~$30.00 AC Delco# 213345