So, the dealership is trying to charge me $300 to replace the thermostat in my 2008 Mazda 6 (2.3L). The thermostat assembly is only $50.

I've been searching online and read that "The Mazda 6 is available with either a four-cylinder or a V6 engine. The four-cylinder (2.3L) does not have a serviceable thermostat. The thermostat is part of a larger cooling assembly, and must be replaced at the dealership. The V6 engine (3.0L) does have a serviceable thermostat."

My question is: Can I just buy the assembly and replace it myself? And if I can, where would I find instructions on how to do so?