Safety first with springs, after you remove the suspension legs from the car you'll need to compress the springs with spring compressors two on a spring at a time, to remove them from the legs. You have to do this carefully and equally if they come off they can cause a lot of damage to you or your car. Other than that you'll need a selection of tools jack axle stands etc
Its a technically straightforward job but you may come up against a lot of rusty siezed nuts and bolts so soak everything in wd 40 repeatedly for a week before you start. Do a thorough search on suspension springs shocks etc and you'll get an idea of what your up against.
You may also want to consider changing the shocks, and or topmounts / bearings at the same time, as lowered springs on old shocks will wear out old topmounts.