Tommy, I'm sorry that your question seems to have fallen through the cracks like this! I know relatively little about yews, since they don't grow in my climate, but what I do know about general transplanting is yours:

The tip you got about pruning the roots first is a good one--I would cut them with a sharp spade about 1/3 of the way to the edge of the canopy all the way around, and along the wall of the house. The root ball you dig up later will be just outside of that cut.

At the same time, I would prune off 1/4 of the foliage, to help keep it from going into shock, though the cooling weather will help with this. When you actually dig it up, prune a little more off, again for shock.

A good root stimulator can be a life saver for a transplanted bush. Ironically, one of the best natural ones is made by soaking minced yew foliage in cold water overnight! Seaweed extract and commercial preparations such as Superthrive are also effective.

One of the essentials of transplant survival is keeping the root ball together and moist while moving. Definitely dig the planting hole before digging up the bush, to save time out of the ground. If it's just going a short way, you can bind it together with cloth, and drag it over on a tarp. If it has to go farther, set it gently on a piece of burlap big enough to entirely wrap the ball, and parcel it up well with natural string--jute or hemp. Once you get it to its new home, you can leave it mostly tied up, though you should open the top for watering, and the wrapping will decay over the next year or two, but it will establish quicker if you can get the wrapping off once its in the hole.

Don't plant the bush any deeper than it was in it's original spot!

And, finally, water well and consistently--every day for the first week, every other day for the next month, and twice a week for the rest of the summer, maybe once a week if the weather is cool.

I hope all this helps!