Storing Vector3's and Detecting Gameobjects

I have thought of a way to implement an A* pathfinding algorithm, and my question was, how could I store vector 3's in a list? For example the closed set and open set. I need to be able to change (1,0,0) from open to closed after being traversed. But more importantly, I was wondering if there was a way to detect if a game object (cube, wall, etc.) was on/covering a point in the 3d environment, so my AI doesn't walk through walls. Any suggestions? Thanks.