a great starting point is
http://www.kernel.org/ it has links to some great how_tos and compile the kernel. The kernel is the heart of linux system it is compiled to the processor used. A distro is just all the packages and directories used. Great pratice and reward is to put linux on an old PC and build a kernel for it. all the tools are free and usually come on the install cd for linux(basically any distro) I personally like mandriva but since all the work is in UBUNTU that would probably be a great place to start. The great thing about linux is everything is free. You can teach yourself from compiling kernels to system administration by just reading for free! You can boot linux from several different kernels, so you can try to boot a new expermental kernel and if it does not work, you can reboot from the good kernel, and I have had many crash and just totally hose out!!!!! But I was so happy after I compiled my first working kernel!