I know this may be somewhat an easy job for some people, but I have never changed a thermostat before. I am some what of a beginner in automotive stuff. I have a 1970 Mustang with a 302 V8. It also has a compresssor for air conditioning. When I took my Mustang out for a drive 2 weeks ago, the temperature gauge was a bit higher than usual. I see no real signs of overheating, but I have come to believe that the relief valve on the thermostat has been activated. I am going to try to change out my thermostat, but don't know what to expect when doing so. I have the tools to do it, but just don't know how to approach it. In addition, I don't know how to properly drain the radiator without making a mess. How should I approach this and what steps should I take?