Re: new to the board, have a few noob questions i'm sure have been answered.
Someone else will come along soon to answer your first two questions but I can help you with the last.
Do not use cork.
It sounds like you bought the same sampler pack I did. The only one that has held up worth a darn is the rubberized high heat fibre (or something along those lines) and even that got brittle after a hundred miles or so. I don't know if it was about to fail but it was hard as a rock when I took the parts off to track down another problem. I haven't found an appropriate replacement available at the auto parts store but a very generous someone is sending me some "super gaskets". Hopefully someone else will chime in but I just wanted to warn you...
...do not use the cork.