I would keep Vegas at your stable as long as possible. When you start riding him you will really appreciate having the BO and stable friends around for support when issues arise (and they will, practically nobody gets a new horse and never has a single issue to work through). Also, usually stables will have bigger/better facilites to work your horse in like an arena and/or roundpen to school and continue your building your relationship with your horse. Even though your goal is trail riding, you will have a stronger, safer relationship with your boy if you work in the arena just as much as you go on the trail at first. I have a great trail horse, but even in the height of trail riding season, we school in the arena at least once a week, more in the winter, and much more when I first got her.
Ideally, IMO, you need to be able to easily move all five body parts: atlas and axis (head, neck vertically and laterally), shoulder, middle and hiney quarters. You would want to be able to walk trot and canter as well as know your diagonals and leads. Also be able to back your horse quietly and correctly. That, in my mind would be the bare minimum, and there is all kinds of additional arena stuff to work on...you can always be a better rider and always build a better horse. It sounds like you are already well schooled taking lessons, but be sure to carry it over when you start riding Vegas.
Trail riding is my passion...I have done it for the past twenty years, but I really wish I had realized the benefits of continuing education for a trail horse in the arena earlier. I had to do it with my current mare if I wanted her to be well-rounded..., she was only four when I got her, and working with her made me realize how much better we got to know each other when schooling....it just made our trail rides all the better. I see many trail riders who have problems with their horses that would really improve if the just did some good schooling with a good instructor.
Good luck, keep us posted!