Not even close. Should be 1/2 hour at most. Drain coolant, undo two bolts, clean gasket surface, install new one and re-fill radiator. Get a second quote.

some of the smaller 6'* are difficult to get to, this may be one of those. i remember having to take the throttle body off to get to the bolts on my buddies grandam

On the 3.1 the thermostat is behind the crossover pipe. I just replaced the one on my malibu. It is a pain to get to the bolts and takes some messing to do it. I also had to remove the crossover pipe shield to get anough clearance to get the housing out over the thermostat. It not really hard just in a tight area. You have to remove the air box first.