I presently have a one (1) light / single switch hookup in the garage. I would like to piggyback off this switch or light (whichever is easier) in order to ADD two (2) 4' Fluorescent shop lights. Can I do this, and is it hard to do?

Yes this can be done, best to connect to the existing light and extend that circuit to the new light outlets.

How hard it will be to do will depend on the existing conditions and your abilities.