►►There are lots of online resources a GM can use for pathfinder. Wikis, and apps for tablets.
I would definitely suggest having a couple months of tabletop gaming experience before trying to be a GM. If you've only played RPG video games, you will essentially be calculating all of the various events, stats of enemies, and rolls/saving throws that the video game does automatically behind the scenes in the program.
It also takes a little imagination and descriptive ability. Unlike video games, this entire world exists in the minds of the players. Its up to you, as the GM, to make sure they are seeing similar things. Where the campaign you're running may have minimal detail laid, its up to you to embellish. Instead of saying "Castle stands to the west" you will need to embellish that with what YOU are imagining. Such as "An imposing black castle with many turrets stands to the west. As you approach, the gate stands 40 feet tall, with heavy chains and menacing teethed gears to open it."
You mentioned that you were a bit shy. That's okay, but being a GM may get you out of your comfort zone. If you've ever been in drama, its kind of like playing improvisation with voices. The gruff dwarven smith isn't going to have YOUR voice, he's going to have a burly, possibly slightly scottish tone to match his character. You'll provide voices to the NPCs of this world.
Essentially, you are the one man band that is going to make the world you are presenting more real, and immersive. Sometimes that means acting downright silly and ridiculous. If speech and drama classes scare you to death... being a GM may not be for you - or its perfect to hone those skills that usually make you uncomfortable.
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