How do you "lower" a truck that had a lift kit put on it?Do you have to redo the whole frame?

What kind of truck and how many inches where added. It may just be all u have to do is buy sum new springs/coils/shackles and shocks, but if the truck was lifted a large amount there may be sum cutting and re welding required

If it was just a body lift, all you do is remove the lift blocks from beneath the bed and reinstall the bed bolts.....basically the same for the front. No frame or suspension work for body lifts.