Motor mounts location and replacement

Hello, I have another question for you all about my van.
First off, I want to thank you all for the help you all have given me over the last couple of months. Can you all tell me step by step how to replace all the motor mounts on this vehicle and where the motor mounts are located. Every time I stop at a light or stop sign, the van has a shaking like the motor is still missing. I finally gave up after all the other repairs and checks I have done over the last couple of months, so I took it in to the local garage here. The guy there told me that the motor mounts were shot and needed to be replaced. He told me that there were four (4) mounts and they needed replaced. He gave me a repair price of $860.00. I think he was trying to get to me because I am a older person. Am I right or is he right?