The buildings have 4 floors and do have elevators. The elevators are located in the center of each building, so could be a bit of a walk to the end units. We have been assigned these a few times, and it is extremely quiet. There are stairs in multiple locations as well, and it may be quicker at times to use the stairs going down, rather than walking to the elevator.
The Springs is the section closet to the the main buildings/pool/fitness center/spa. The caveat with that, is that it is the last bus stop on the route to and from the parks. There may be times that you might actually have to wait for more than one bus, as we have seen them fill up in the morning, and have to skip the Springs. This would cause you to wait possibly 30-40 minutes for a bus in the morning. Of course, once the early morning rush has died down, there usually isn't a problem.
Saying that, we have always requested and stayed at the Grandstand. It is the first bus stop when dropping off or picking up for the parks, so you are pretty much guaranteed a seat in the mornings, and you are first off on the way back. The bus stop is a very short walk from any building. It has it's own quiet pool with a pool bar that is open during the day. The main area is only a short < 5 minute walk, even from the outermost building.
If you are looking to walk to Disney Springs, then Congress Park is the closest, though can be a bit of a walk to the main buildings.
Good luck!! I know you'll have a great time there!