About 15 years ago i just started installing it and using it for various tasks. In a smaller company this is a very easy thing to get away with, and I've spent most of my career in Small/Medium businesses. Many of which were in startup mode and saving money was an easy sale. What makes you a professional is when you've started to break things, or see things fall apart and you can fix it.
The hardest part about Linux (or at least was) is that you'd have to cash the checks you were writing, no blaming microsoft or Oracle when you put Linux on the line.
Any chance that you have to get an organization to invest in Linux is a sign that they are interested in investing in their own employees, namely you.
If they aren't interested in trying Linux/Open Source, it's probably trust issues with turnover or having been burnt by someone in the past that just didn't know what they were doing. If you do jump into that game, start with something small and low-key, maybe a simple PHP app or a file server. Ease into other services and build up your toolbox. You will panic the first time the disk fills up, or the server is unresponsive and you have to mount the disk in single user mode for a repair. Things happen, but lucky for you google is your friend.
The best way to become a professional in my experience is to jump in and Just do it !
Best of luck.