@jonathan7:i would never use same footage or shots from other movies for the sake of story telling or executing an idea.I prefer take time and devote of making something new.
@Darth_Ender: The background replacement is easy with some more post work on it. Some one has to roto out luke and other elements for sure.
About the removal of the lightsaber. In some shots can be done with some smart patches but they will not work on complex shots like when cloths are moving or bending. You have to count the shots that he has the saber and decide how much from them will you cut,reframe or remove the saber just to start managing the work and each one can take its task. :)
-Angel