How long does it take on an average to change a thermostate ?

What is your question?

My van continues to overheat more and more everyday which never started till the weather dropped down to around 25 degrees. It seems like the distance I can go before I have to pull over and let it cool down is becoming less and less. I have been topping it off with antifreeze everyday but it doesn't seem to help at all and everything I put in it seems to disappear into thin air. I have a new thermostat for it but nobody wants to put it in because they say it's a pain in the but as well as a 4-5 hour job......