I took my car to the dealership for diagnostic and they told me I need to change this out along with the power steering pump that is leaking for $1100. What does this vaccum switching valve do and how hard is it to replace. TIA

The price is sound about right for the new PS pump and high pressure line( which included the vacuum switching valve). The job is moderated, but you have to know what you are doing and quite a few tools. Plus you have clean the steering rack solenoid and clean the screen at the PS resorvior. You do some search about PS pump and I'm sure it will be over 50 times that this topic had been discuss in the past.