In the Thermostat Replacement DIY (link) the use of gasket maker is described. Do I need that if I replace the rubber thermostat gasket? That is, do they serve the same or two different purposes?

The Honda service manual gives a testing procedure for the engine coolant temperature (ECT) switch on the same page as the test procedure for the thermostat. My 96' Civic has 90K mi on it. I'm due for a coolant change and I plan to change the thermostat because I doubt it has been done. Does it make sense to replace the ECT switch at the same time I replace the thermostat (even though neither is broken)? I don't know the life expectancy of an ECT switch. The cost for a new one at my auto parts store is $18.

Thanks,
Scott