First off is this something you can do yourself? And as far as changing the heater core hoses thats BS. All you have to do is remove the clamp, grab the hose and give it a twist to break it free from the heater core line. Then just twist and pull back at the same time and viola! you have removed the hose. Obviously you don't want to hulk up on it as the core is thin metal and "could" break a seam, but if you are carefull you should have no issues. Done this for years and have yet to cause a leak.
And that .7 hours is book time. You will get billed that regardless of the 30-45 min. it takes to change those 4 hoses. The longest part will be refilling the system w/ coolant and bleeding all the air out of it. That I could see taking a good solid hour.
