FASA Games, Inc.

4th edition will be my first edition. Unfortunately, I'm a bit of a perma-GM for my group. When the players guide releases will that document allow me to learn and start running games? Or will I need to wait for the GMs guide as well?

If you've GM'ed over the years and used a variety of systems I would say you probably have enough knowledge to go without waiting. You would be missing creature/horror stats and game-specific ways of handling things, but an experienced GM can work around those easily enough. Know that the step number for what your players are rolling is their average roll. Set difficulty numbers based around that knowledge.

You could always pull information from 3rd edition (or any of the other 3 besides 3rd) if you felt you needed world specific information. Most of the information is going to be functionally identical (spell defense became mystic defense for terminology is all).