Recently my check engine light came on and then I started to notice the car wasn't getting as warm as I'd like it. I took it in for an oil change and they diagnosed that the thermostat (at least) needed to be replaced. I called the Volvo dealer and they gave me a price of $365 and indicated that other sensors might need replacing at the same time. Is it really that big a deal to replace a thermostat and is that a fair price? I know they will try to put in new O2 sensors if they can get me to agree. Should I agree? They haven't been replaced and the car is 5 years old now? Appreciate any feedback! Thanks!