Why do you think so? I think it's just comes to practice and doing your best that's all. Being a GM isn't exactly stressful as one might think. If your RPers play well and clean and all are fun and active, no matter what role you serve as, roleplaying will eternally be fun and joyful! :)
I'm still not too sure about how you're going to wrap the story together with having players start... all over the world? Are you going to act as a GM and give them events and enemies, or are you going to bring the players together somehow?
Here it's also a matter of loose story. It can work, but I wonder if people know what to do if they sign up for your RP. I'd feel a bit lost. But if you feel like you know how the RP is supposed to be played and go about, then I'm sure it's gonna be interesting :)
For a beginner, I suggest trying for a spot in those RPs that have newly-experienced GMs as they won't be very strict on you. Also, find one that isn't too fast for someone new like to catch up, unless you're confident or don't mind. :> Lastly, you should pick one that suits your favourite genre of RPs so that you could ultimately have fun. :)
