I'd say around half an hour sounds about right. You have to drain some antifreeze, change the t-stat, refill the antifreeze, bring the car up to operating temperature, and burp the cooling system.
wait untill you do one like on my 03 cobra.. it takes more time to get under car than to replace it...its in the lower hose and bolts are in your face...soo easy but still half hour with beer in hand