Sorry I didn't get back earlier. The questions you need to ask will come naturally. Talk about your expectations from a guide trip and you will pick up a lot. The answers will not be in what the guide says but how they say it to you. It is all about their communication style and how they adapt to you. There are few personality types that I can't teach but they do exist. Most guides are not in the business because they have great personalities. You want a guide who works well with you and can adjust to teaching you the way you learn. That is the toughest part of finding a guide to teach you fly casting/fishing. For example, when I talk with clients about winter fishing I am honest and tell them if they touch a fish they are pretty lucky. But what they will get from my trip is an education on the when, how and why of what the fish are doing. If things are really slow they will get a casting tune up regardless of their skill level. They will learn something during the day and more often than not they will hook a fish.
The old adage "Give a man a fish and he will eat for a day. Teach a man to fish he will eat for the rest of his life." works very well here. But, in your case teaching you to fish before you have casting technique can trap you in mediocrity. A lot of intermediate and some advanced anglers I guide have difficulty casting when the chips are down and they are focussed on fishing. Every bad cast they make sets them back as a caster, especially if it results in a fish. This knowledge is why I am so good at what I do. I analyze the anglers skills, give them the tools they need and have them focus on those tools and skills. Meanwhile, while they are focused on their casting skills, I place the boat where their skills come together with the fish. I have anglers focus on making good casts whether they are 15' or 50'. My job is to get their cast into the zone so they catch fish. The exception to this rule is when I get a complete newbie who I know will never flyfish again. Even then I teach them a water loaded cast and put the boat where their presentation can catch fish. They catch fish and go home happy, they don't need, or want to learn a new skill.
To truly advance as a fisherman, to really focus on the when, how and why, the casting part of the equation should be almost automatic. When casting is an after thought you can look at a piece of water you know will hold fish and hit it automatically. You can focus on what the water and the fish are telling you. The mends come automatically and your fly gets exactly where you want it. Your focus is on the fishing not the casting.
An example of the flip side of that coin is a world champion caster a good client brought on a trip. The first thing he said to me when I met him was "Steve, my goal today is to learn one thing from you." I thought "oh boy, here we go.." The first spot we stopped to fish was a great spot I knew well. I walk the caster into position and told him how to fish the spot, start close and work your way out to the sweet spot. He stripped 100' of line off his reel and sent the whole thing across the river. He looked at me with a big smile and said with a smirk "What do you think you can teach me?" I told him "you will never catch a fish casting like that. The fish you want to catch is 25' in front of you." The next cast he pulled back to 50' and cast strait across the river. I told him to bring it in to 20' and cast quartering down, spey fishing, because I wanted his fly fishing the second it hits the water. His response was "thats not how I fish!" I simply told him that he has made two casts and he has learned a number of things. First fish where the fish are not where you want to. Second if you can't adapt to the situation you will fail as an angler. Finally, if you hire a guide you listen to them otherwise you are wasting you money and his time. I spent the rest of the day helping the other angler...
Fly fishing is what you make it. It can be a challenging new skill to learn and perfect, or it can be something cool to do on occasion. Never forget to look at the beauty that surrounds you and relax. Enjoy the whole experience and let it recharge your sole.
Best of luck to you.