Most diecast models have bodies of cast white metal, while the rest of the model (chassis, engine, interior) is usually plastic. Working with a diecast body isn't exactly the same as working with plastic bodies.
You need a power tool (Dremel with a cutoff wheel) to make cuts in the body... using a razor saw and making cuts by hand is possible but labor-intensive. Joining cut metal parts requires epoxy instead of styrene glue. Body filler (Bondo, for example) is the best thing to use for filling seams, creating contours, etc. Just about any paint can be used, just prime first. The rest of the plastic parts can be worked pretty much the same as a typical plastic model kit, but sometimes the plastic used in diecast models is a different type than the plastic used in typical plastic kits, so you'll need a different glue (CA or epoxy) instead of styrene glue.