Hi Thomaslee! Maybe I can help, what's intimidating for you? Maybe I can explain it so you can understand it better and then its not so scary after all.
Best thing I can tell you if you are going to be a game master have a general out line of what you want the characters to do. Then add in off shoots to cover any possible choice they might make. Even then you can have something you got to come up with on the fly but you can make it work with general stuff prepared and then fine tune it as they go down a particular path. As they go you can add in other things that they may want to keep in the back of their minds to figure out that can make it more than just go here kill everything then go back. Make it turn into a story that they can tell their grandkids.
Plan ahead plan ahead and then plan ahead. I can offer some advise too if you need it.
I understand your position. I suggest you join in a game first to understand the new format which might be different to what you may have known. This will help you get familiar with the character creator, etc.