Mystery vibration at 25 mph can't be diagnosed. It's not the front end!

The shop is right. The washers are not a "fix". They are a diagnosis tool. Listen to Dan. He is not blowing smoke up your skirt. Get the books he recommended. Read them. Learn how to diagnose and repair your car yourself. These things are like Fred Flinstone compared to new cars. A chimp can be trained to disassemble and reassemble them. It's not difficult. There are no magic tricks. There are no unknowns. You can learn to do every single diagnosis and repair all by yourself if you will simply listen to good advice.