That tech is feeding you BS and only wants to rob you of your money for work that does not need to be done. Valve cover gaskets do not need to be replaced unless they are showing signs of leaking and are not considered to be a mainenance item. As for the “all the seals in the car” thing, once again I would not replace anything unless it shows signs of damage or leakage. That tech is just trying to make money off of you, at least in my opinion.