1990 Toyota Corolla, 190,000 miles, 4 cylinder, 5-speed

I was driving down the road when I heard what sounded like mud being thrown off of my front passenger tire. I stopped but couldn't find anything caught on the tire or axle.

The noise continued even when stopped with the engine running. After a few blocks, my steering went out completely as if I no longer had power steering.

I arrived a home, popped the hood and looked under the car. A belt was hanging underneath the car near the front passenger tire.

There was no warning that the belt needed replaced. It appears to have separated and become hung.

I would like to replace the belt myself. Can you tell me what kind of belt I should purchase? Should I have a mechanic replace the belt instead of me?