Since your a tech and like to "roll your own," my suggestion if you want to
learn GNU/Linux inside out is to split your drive into at least three
partitions, a small boot partition ~20MiB and two main partitions for
experimenting.  Get some mainstream distribution loaded onto one of the main
partitions, RH, MDK, SuSE, or Debian.  Then go to
http:://linuxfromscratch.org and do an LFS install onto the other partition.
This is at an even lower level than Gentoo, but by the time you have done it
you will understand the entire boot-up/init process as well as
accounts/groups and file permissions.

Linux From Scratch is pretty much what it sounds like.  You format a
partition build the kernel, copy files to the new partition, create
configuration files, startup files everything yourself following the book.
When you are done you have a bootable system that you have created from the
ground up.  This really gives you a good understanding of the basics of
where to find things and how to change them in Linux.