If the vacuum is working fine, do not change it. There is a o-ring on it, that can be replaced a lot cheaper. I say if you change the valve cover gaskets, change the timing cover gaskets while you are that far. You will have to remove the vacuum pump, to get to the passenger side timing cover off. The valve cover gaskets are a PITA, but doable. OEM valve cover gasket's are 80.00 each, aftermarket can be found for 40.00 each. Timing cover gaskets are 13.00 each. Dealer will charge from 800 to 1200 labor for valve cover gaskets. Timing cover gasket labor while changing valve cover gasket, around an additional 500.00.
I can not stand oil leaks, so I did all of mine. I don't really want to pay the dealer 1800.00, for work that I can do!
Hope this might help!