We have a picture window approx. 4 ft. high and 6-7 ft. wide that needs replacing. What is a median price range for this?

I would shop for your own window, by brand that you want.
Vinyl covered wood is pretty common.
Then pay 2 carpenters for installation and all other materials. Plan on a day's work or at least most of it, depending on the condition of the trim and flashing. By the hour might be good if you don't know what will be found in the way of rot around the edges. Ask for either quotes or estimates. If it's all very clear what shape it's all in, get quotes. Not just 'install window,' - you want it to specify the steps. And disposal of the old window and all debris. You can get prices of windows online at major manufacturers like Andersen, Marvin, Pella, etc (last 2 very expensive). Winter time carpenter rates might be $40-45/hr per person, at least where I am, but it varies by where you are. You might get someone with a helper who costs less.

OOPS! Andersen doesn't publish their prices anymore. Plan on high hundreds, I think, for 4' x 6'6. I have no idea, but I bought a whole house full of Andersen 2 years ago, but no picture window. Plus prices vary by model. Visit a good lumberyard.