I ordered a belt, an idler pulley, and a motor pulley. I watched the repair video. When the parts arrived I followed the video and changed out each part. While the dryer was open, I put an adjustable wrench on the blower shaft and turned the motor. The two turned separately, to my surprise. At that point, I realized the blower wheel was the real problem. Again, I watched the video for changing the blower wheel and ordered a new one. When it arrived, I very quickly changed it and reassembled the dryer, and started it and it was so quiet. The only components not changed were the drum rollers.
I am TOTALLY pleased with the service, price, and installation videos provided by AppliancePartsPros.com. They have given a ten-year-old dryer another ten years of life.