Peace of mind is a good thing.
When I had the whole cooling system replaced due to seeping radiator and unknown timing belt history, I ordered and bought all the parts myself online and at the dealer with coupons. it came out under $550 for all parts including tax and shipping.
I then asked a couple of independent mechanics for a quote on labor. One mechanic liked that all the parts were quality parts like aisin, denso, bando, Mitsuboshi, and Toyota. He did it for $500 total labor.
cheaper: buy the parts yourself, find a good inexpensive Indy mechanic to do the labor.
cheapest: buy the parts yourself, install yourself.
Parts included: red coolant, radiator, rad cap, thermostat, water pump, timing belt, drive belt, upper/lower hoses, pulley.