Welcome to the Site. I've been here for about a year and keep finding more here about myself and erotic hypnosis all the time.
Induction files, as dhardin said, are intended to induce hypnosis and usually little else. Many, like Lutz's Bubble Induction, will install a trance trigger to bring you back into a hypnotic state, but most do not.
As you are just starting out, you may want focus on trying different induction files to see what type of induction seems to work best at bringing you comfortably into a state of trance. Then, maybe focus on one induction file (and possibly another file with a simple effect), using it at least once a day, almost every day, for a couple weeks or so. Most people find that if they use a well-made hypnosis file for 2-3 weeks, they will see results from that file.
Since you have already experienced hypnotic trance, you probably already have a good foundation to build upon. That means that you will find that you can more easily reach a deep trance state because it's someplace you've already been, so it's easy for you remember the way there. It lies in the same direction as fantasies and daydreams, which means it's a very nice place to go. For the next couple of weeks, focus on just enjoying "The Journey" and let the files you choose worry about exactly when and how you will reach your destination.
During this time, be sure to check out WMM's sister site for "social networking",
Hypno-Fetish, where you'll find interesting people who may be into helping you and your wife learn more about the "scene". Your fantasy is a fairly common one, disenchanted, so I'm sure you'll find it an easy one to explore using hypnosis if you proceed diligently toward your goal.
Most find that erotic hypnosis is practically perfect for fantasy fulfillment because it almost has "safe, sane and consensual" built right into it and, since you already have a relationship with some established trust, I'm sure you and your wife will have lots of fun exploring your fantasies together.
Calimore