Yes, if it gets bad enough. The oil will soak the plug wires. Buy a valve cover gasket set. It will come with new seals. Very simple deal.
If you buy them from the dealer, they sell them separate. But FELPRO has a kit that you can get at auto stores for $40-50 that includes the vc gaskets and the spark plug tube seals.I did NOT get spark plug seals when I bought a pair of valve cover gaskets. It can cause mis-fire, but I don't think it would keep the car from starting either -- except maybe on the 4-banger, where it would make more of a difference than on the 6.