I would say MINIMUM 3 hours of labor. I work at a Ford dealer and that is probably close, if not too low, of what I would quote a customer.
My MM full lengths took me almost 6 hours to get completely installed. A lot of tweaking, heating, and measuring to make sure everything is right and square. You have to remember that any shop charges that much labor because after any job is done, any good shop will realize they now "own" that job. If anything is wrong with it, they MUST fix it.
My advice is find a friend or go buy a welder. My Craftsman does did just fine with flux core, but setup as a MIG does much better.
1991 Mustang GT Vert
"Life is tough....Its tougher if you're stupid"