I can't answer re: First Choice, but the benefits of staff travel in the travel industry (long haul) have been eroded by the massive imposition of fuel surcharges and taxes, as we only get discounts on the base airfare. I can normally get to Asia on a decent airline for about £300, which isn't a massive perk, but I often get freebies, just without the family!
Re: any travel interview, brush up on the geography of the core destinations you'll be selling. Smile, show enthusiasm, and remember at the end of the day, if it's a sales job, your job is to sell, so maybe think of examples in the past where you've utilised this.
A willingness to help, match perfect holidays, problem solving, and the willingness to learn are all important. As are the ability to laugh off long hours, pathetic pay, constant derision from the general public, daily bouts of rudeness from your clients and complete lack of support from your bosses (unless you happen to be a shareholder as well), then you should do fine!