$475 Reasonable for Thermostat Replacement?

I have a check engine light on in my 2002 Audi A4 1.8 (106,500 mi) and the error code is P1296. Had this code back in January and got a coolant temperature sensor replaced which seemed to solve the problem for a while. I took the car into the shop and they said a thermostat replacement is needed now. They are asking $153 for the thermostat and $310 for 2.7hrs of labor ($475.83 after tax). Does this sound reasonable (seems pricey to me!) or should I call around? They said it is a "very difficult" thing to replace. Picture of estimate below. Thanks!