For the VC gasket, here's all you need to do. Easy. Leakproof. And the gasket will be re-usable for a long time.
#1. Remove old gasket and get the gasket mating area on the valve cover AND head squeeky clean.
#2 Apply an even bead of a good RTV sealant on the mating surface of the valve cover. Put the new cork gasket on the valve cover, flip it over, and put it on a flat surface with some weight on it for a few hours. Overnight is better. Youare basically gluing the gasket to teh valve cover with the rtv.
#3 Here is the important step. Before you re install the valve cover and new gasket, put a thin layer of grease on either the head or the vc gasket. It's easier to put it on the valve cover gasket which is now nicely glued to the vc itself. So you want a thin layer of grease between the head's mating surface and the gasket (which is glued to the vc).
By doing this, the valve cover can be removed as often as you like, and the gasket will not stick to the head. The grease probably does a small bit to help against leaks too. Just be careful not to overtighten the vc bolts.
Hope this helps. It sure works for me.
codfish