I dont know what the heck I was writing, now Ive confused myself
Ill look when I get home.
No need to drain the oil, it drains back to the pan. A small amount will be still inside the valve cover, just put a few paper towels under it.
Im pretty sure the bolts you speak of are 12 sided. A majority of tools are designed to fit them, usually you have to specifically get 6 sided.
I seriously suggest replacing both at the same time. Even if the other side is not leaking.