A friend's dryer was squealing. It was the idler pulley. I lubed it but I was sure it would only be a temporary fix. Sure enough, a bit later the drum would not spin. The metal bearing in the pulley fell to pieces. The shaft it sat on was scored. We decided to change the belt while we were at it.
The first video I watched was on Appliance Pros. We used it as a guide. We had a bit of trouble getting the front control panel off since our model differed a bit from the one in the video, but we figured it out. The whole job took about 1.5 hours, but we cleaned the inside really good while we had it apart. Taking a few pics along the way was helpful....it's easy to forget where a certain size screw goes or where a cable plug should go once you remove it.