Regarding lhoang's original post and model, have a look at the attached PDF. It might not be everyones prefered workflow, but it's pretty simple to follow.
You could import the IGES file as an assemby of parts, but you nearly always strike one part (as in this model) that needs breaking up into sensible sheet metal bodies. Bringing the IGES file into a single part environment lets you break the model into the required bodies before creating the sheet metal parts and you get a much better understanding of the design intent if you see everything in the context of the finished assembly.
Hope it helps.