Hi Mad

I just looked in my Fallout 3 manual, and basically interface works like it did in Oblivion (if you can play this game?) [Bethesda that made Oblivion also made Fallout 3, so this really isn't that surprising].
You move with the wsad keys, activate via the the 'e' key.
However, when you press the V-key, you get into VATS, which is sort of like pressing space bar (in combat) in Baldur's Gate 2
And I wouldn't call Fallout 3 a first person shooter, especially since you can play in a very nice third person mode. Its is a bit difficult to explain, but when you hit V, the game will pause, and you can use this mode to select an enemy. You can also use this mode to select a special body part, say the head, arm or torso...
You can also, as I recall? attack with the left mouse button as well as aim/block with the right mouse button.
AN FPS game to me is more like Call of Duty where it is your aiming skills that determines whether or not you will hit your target. In Fallout 3, it it is your character's skills that will determine whether or not the character will hit or not. [This is modified to an extent in Fallout 3, I think you'll always hit? but the damage done is depended on your character's skills]
And you can use an Xbox 360 controller...