At the top of this forum is a sticky thread that called "DIY index." In there you will find a link to a thread about changing you oil.
Here is a link to the index thread, I know the oil change is in there somewhere...
DIY/install index - LOOK HERE BEFORE ASKING FOR A DIY
Ahhh... the oil change is for a normal civic. The procdure is the same for the Si, but the drain bolt and filter are in different locations. The drain bolt should still be at the bottom of the oil pan, but the the filter is more towrds the back of the engine by the firewall, I think it up higher too and side ways. Can someone else confirm where the oil filter is? I don't have an Si....
Good luck and hope this helkps!