If you want to replace the springs while you're in there, support the back of the car and carefully cut them with a torch. Lots of big bangs and sparks, but it's not as dangerous as it sounds.
When you buy the new springs get a spring shop to compress and band them for you. Once everything is back in place and you have the weight back on the springs cut the bands and away you go. They can band them straight or with a curve, whatever makes them easier to install.
The only thing to worry about is if the bands break on the compressed springs while you are handling them. It's only happened to me once.
