Mechanic Job in Riverside, California

I have a 2006 dodge magnum sad kept overheating after I got my vehicle flushed from Valvoline I brought it to a shop and they said that it seems like I need a thermostat but they wanted $250 for the job I don't know if that's normal or not but it sounded kind of high to do the thermostat I would like it if somebody would be able to fix it for me today and be honest with me on the pricing as I am limited as to what I can spend they also were not able to do the job that day so which means I would have had to get my car home and then have it towed to them which I could not afford to do