There're tons of tutorial and shaders on the web, here is one I found most useful.
http://www.drone.org/tutorials/normal_maps.html
Haven't used normal maps in Maya 7 but my guess is it's the same.
*** Just checked with Maya 7, now you can use a bump node and select "Use as Tangent Space Normals"
Or you can just down the js_normalmapper from
http://www.pixero.com/