how hard is it?

It's pretty easy to do, I'll tell you how I do it. First, I'll give you one piece of advice: After the car is on jackstands and before you disconnect ANYTHING, make sure you also put a pair of jackstands under the rear axle. The whole rear suspension is pretty much interconnected. As soon as you disconnect your first bolt, the rear axle will SHIFT and you'll have a real hard time trying to realign everything.

What I do is: I put wheel chocks in front of the front wheels, then lift the rear of the car with a jack under the differential. I put a block of wood between the jack and the differential to spread out the weight (otherwise, you can damage the differential with the jack). I put jackstands under the rear jack points (notches in the pinch seam under the side skirts), and let the jack down most of the way. Then put jackstands under the axle on both ends, as close to the wheels as you can. DO NOT put the jackstands in the middle of the axle tube! They're not designed to take that weight in one spot and you can bend the axle tube. Now, let the axle down all the way. The axle should now be resting on the jackstands; if you can wiggle the jackstands at all then raise the axle up and bring the jackstands up a notch.

Do one part at a time, remove it and install the new parts before moving on to the next one. This will help keep everything aligned right for installation.

Put a jack underneath the lower control arm when you remove one of the bolts. Lower the jack and you'll take all the pressure out of the spring; it should just fall out. When you install the new spring, make sure the end of the bottom coil is pointing to the driver's side of the car, and make sure both springs are pointing the same way. If they're not, the rear of the car will NOT sit level.

If these bolts have not been removed before, they're going to be a PITA to remove. Good luck!