The first step is to want to, and you've definitely got that covered. Reaching out to the community is more than most people do, and will give you a lot more perspective and insight than those people who don't.
Systems administration might be more accurately thought of as the care and feeding of data. We're essentially data wranglers, and most of our time is spent moving it around or making sure it's available to the people who need it. To that end, I suggest that you become very comfortable with moving files around a network using things like rsync, cURL, and scp, and making files available to various services like HTTP, FTP, Samba, NFS and the like.
I also suggest that you practice backing up your data and restoring it. Bacula and Amanda are good enterprise-ready free backup solutions, so take advantage of that. I believe that both (I know Amanda does) can deal with virtual tape libraries, where you have a disk image that acts like a tape, and software that acts like a tape changer. It's important to learn how to deal with that, because almost all large backup solutions use that concept. Having a viable backup solution is the art of saying "what if..." and having answers.
Overall, you're doing great. The only thing that I can think of that you'd need to know that you aren't virtualizing is networking equipment, and you can fake that by using routing simulators or even picking up virtual machines.
Good luck, and come back with more questions!