Thank you Ernio, but I'm still a little confused on some things.
First, to clarify, I'm assuming when you said I wasn't overriding the "real" method that you were referring to the ones in GuiHandler.java. Am I correct in this assumption or were you talking about something else?
Second, I made the last change that you suggested about running player.openGui() on !world.isRemote instead.
Lastly though, I understand what you're saying by your "2nd mistake" but I'm unsure what you're instructing me to do by informing me of this. If you could get back to me sometime soon, that would be fantastic.
Thank you very much Ernio