You see, the advantages of Micro$oft gear is that the knowledge is out there with regards to the "why won't this WORK???!?!" 11pm google-panic over Exchange etc. It's just not with Linux as the 'entry level' of knowledge is higher. That's always going to be a very persuasive plus.
I've no idea how to apply group policy etc with Linux to Linux clients. I can do some things with skeleton directories and bash scripts but I'd be utterly at sea on a Linux-only network with Linux clients.
We do have some Linux clients that I've put Lubuntu and Gofris on, which essentially just open a browser for the kids and once restarted go back to my 'factory' setting (think 'Deep Freeze' for Windows) but that's it. They're 900mhz and 512mb I think and the fastest-booting clients in school. SEN love them.
I started learning Linux later on in life. Not too bad, have LPIC cert now.
For general advice, if you want to learn it, get a VM and just break it a BUNCH. Don't feel bad, just smash away. For a first project, set up a samba server with winbind so you can restrict access against AD. That's useful and 'feel good'. Then maybe tackle the CompTIA Linux+. You'll find each stage hard going but persevere.
Linux is really frustrating. I'll say again, REALLY frustrating if you're used to Windows, but don't let it make you feel stupid as you learn. You're not stupid. Linux is.