What I don't know about rugs would fill volumes. No problem; Ed Momeni at Arizona Rug Co. was helpful and patient. I found the rug on Facebook Marketplace and called. By the time I got to the store, Ed had it laid out. His price was reasonable, including the cost of spraying the rug with protectant and delivery.
Jacob, who delivered the rug, helped me install it. And he hauled the old one away. These things are heavy and awkward. I appreciated his help.
One of the reviewers for Arizona Rug Co. complained that the rug she bought was not the exact size. That is common, according to information I found online. The rug I purchased is nominally 9 X 12. It is actually 8 feet, 10 inches by 12 feet, 2 inches. If size is critical, measure the carpet in the store.