Where do I start?

I work in a RHEL5/6 environment where the RHEL admins are starting to train for RHEL7, but we probably won't move to any RHEL7 units until maybe next year if not later. Now.... I'm on the network side of the house, however, there many tasks that require RHEL work and I'm coming from Windows only environments and need to get familiar with Linux/RHEL. I only have BASIC knowledge of Linux.. like, I've only done some basic tasks sporadically, and with the help of other Linux gurus and lots of Googling. I'm not very afraid of a CLI, but Linux is terrifying, coming from Windows, considering it's ALL command line.
I'm looking into courses on how to get started to catch up, but I'm not sure if starting with RHEL (7) courses will give me the basics I need to know first. (Will it?) There are so many flavors of Linux that I'm confused for where to start and how to practice outside of work, especially since RHEL7 sounds like it's very different from 4/5/6 with the new major updates/changes, and since we're not even using it yet. Before I sign up for something like Linux Academy, I want to know where is the best place to start for someone like me. Any help would be appreciated. Thanks, in advance.
I'm looking into courses on how to get started to catch up, but I'm not sure if starting with RHEL (7) courses will give me the basics I need to know first. (Will it?) There are so many flavors of Linux that I'm confused for where to start and how to practice outside of work, especially since RHEL7 sounds like it's very different from 4/5/6 with the new major updates/changes, and since we're not even using it yet. Before I sign up for something like Linux Academy, I want to know where is the best place to start for someone like me. Any help would be appreciated. Thanks, in advance.
Comments
Take it a little bit at a time so you don't get overwhelmed; use the Linux Academy labs and watch the videos, then look up what you don't understand either in official Red Hat documentation (which is free and publicly available) or using Google.
CentOS is RHEL without any brand images and updates from RHN. However, CentOS is actively maintained by Red Hat developers as well as non-paid developers, so its perfectly reasonable to lab with CentOS if you so choose.