[brucepick]

As for the valve cover - if you've got all the fasteners removed and it's stuck due to the gasket(s) being glued or stuck, then tap it with a mallet, or maybe gently with a hammer. If using a hammer, maybe better to put a block of wood against the valve cover and hit that.

I haven't worked on that particular engine but I've pulled off a couple sticky valve covers in my day.

And another related tip - for screws/nuts that refuse to turn. After spraying with your preferred loosener (I like PB Blaster), use a hand wrench and tap the wrench handle with a hammer. Many light taps, doing manually what an air impact wrench would do. Except you tap lighter so you don't snap the bolt if its a small one. It takes some time but it works.

If the hex is completely messed up, try a vise-grip and tap that with the hammer.