Vacuum solenoid and Forward Heat Shield
 

I took my 2004 Mazda 3 into a a Mazda dealership to have my lock nuts taken off and put on some regular lugs on my wheels.They returned my car to me and told me the vacuum solenoid was not working and the forward heat shield had all but disintegrated.

I need some information on these two pieces. I am not a terrible amateur, so I do know my way around an engine and a car. I need to know how these pieces work, the difficult to replace them, and any other information you can give me.

thanks guys, Zoom Zoom.