I'm going to be at Walmart tomorrow, and would like to pick up some wipers for cheap. They had a wiper selector "computer" that says the driver side is 20" and the passenger side is 18". Is this accurate for the brands they sell at Walmart? It shows directions on how to install them, but which type of mechanism does the Corolla use? If you can point me to any step by step instructions on how to install, that would be great.