Kernel Questions

I'm using a u5 as a firewall, dns among other things. I want to learn more
about working with the kernel. I have anonymous CVS set up. What I think I
need at this point is information on how to tweek the kernel. All I really
want to do for now is to only have what's necessary that I will commonly use
in the kernel. As far as I know this may already be done, I still want to be
able to identify how to do this.

I have a couple scripts that I use to update my CVS, build and move kernel
and build all new binaries.

I need direction to resources that will explain working with these sources?
Thank you.