Suck Out Insulation
Tearing down a drywall ceiling is not a super-pleasant experience, but tearing down a ceiling that has 14 in. of blown-in insulation on top of it is a complete nightmare. Avoid that gigantic mess by sucking out all the insulation in the attic before pulling down any drywall.
The huge vacuum required for the job costs about $220 a day to rent, but if your local rental center doesn't carry them, call an insulation contractor in your area. Many blow-in insulation installers also have the equipment to suck out the insulation. But this service isn't cheap: Expect to pay about $1 to $1.50 per sq. ft. You might be able to get a deal if you use the same company to blow in the new insulation. Make sure your insulation is fiberglass or cellulose. If you even suspect there's vermiculite insulation in the attic, get an expert opinion before touching the stuff—it could contain asbestos.
Cut Around the Window With a Recip Saw
So don't bother pulling the nails or screws out of an old window. Just run a recip saw between the window and the framing and cut the fasteners and the foam at the same time. You may want a buddy on the other side of the window to keep it from falling out when you're done cutting around it. With a long enough blade, you can even slice through the nailing flange at the same time. That's important if you're trying to save the siding around the opening. Learn how to prevent leaks with proper window installation.