Those thing's are hard to quote when you can come up against unexpected add-on cost I.G. water pump's, defective water hose's ect ect.
Like mercury said, they warrent all work done on vehicle, that's where alot of people go wrong, not knocking old mate who wants to do it for $200, but if something does go wrong, not saying it will, but WHAT IF, will you cover the cost of bent valve's or whatever may happen????????
It pay's to be safe, it pay's to do it by a professional with insurance background.