It's very rare to get hired right into Guest Relations, even then you wont start as a tour guide. The ones who do the backstage tours that people pay for and book are the same ones who do the VIP guide stuff.
Over at DL, my tour guide had recently come from working at Nordstrom. High end retail customer service. That sort of background. I didn't ask, but she was probably even a personal shopper or something akin to it.
People can certainly work their way into the job though. Saw college program kids (CP's) go into Guest Relations sometime after working diligently in their original area.