Not sure what you're referring to by emergency brake spring. Inside the rear drum there are two springs: one short one on the bottom which straps the shoes together and one larger/longer one on top which is the shoe return spring. Both are fairly easy to replace but finding a replacement first might be a challenge. To remove the top one, I first remove the "bar" that goes from the hand brake lever mounted on the rear most shoe to the other shoe. Then I use a side cutter to grip the spring, stretch it and unhook it. You don't need to disconnect the hand brake cable (not an easy job).
Let me know if this helps.