I don't want to mess anything
up because I depend on this computer...someone nudge me in
the right direction please?

IMO, the best education would be to install a basic Linux distribution such as
Slackware, Arch, Gentoo or Linux From Scratch. By basic I mean that they force
you do things manually that other distro automate as part of the installation
process. That way you can see how it works under the hood. Once you have a sense
of what is going on when you do something then you can do whatever your mind
wants, including making your own distribution.

However, you mention a sandbox. For that you should have a second computer or a
drive that you don't care about. Install Linux there, but keep it isolated from
your main operating system.

http://www.linuxfromscratch.org/